Diuretic Agents - ACS Publications - American Chemical Society

7 2-Aminomethylphenols: A New Class of Saluretic Agents R. L . SMITH, E . M . SCHULTZ, G. E . STOKKER, and E . J. CRAGOE, JR.

Downloaded by UNIV OF SOUTHERN CALIFORNIA on June 18, 2016 | http://pubs.acs.org Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0083.ch007

Merck Sharp and Dohme Research Laboratories, West Point, PA 19486

A continuing search for new renal agents i n our laboratories by screening carefully selected compounds for diuretic and salu r e t i c activity i n rats and dogs led to the discovery of 2-aminomethyl-3,4,6-trichlorophenol (Ia). The unusual structural fea tures, attractive electrolyte excretion profile and saluretic potency of compound Ia relative to those of known diuretics (see Table I for an activity comparison) provided impetus for an extensive synthetic program. The data obtained f a c i l i t a t e d the delineation of the structure-activity relationships for a variety of 2-aminomethylphenols and culminated i n the development of 2-aminomethyl-4-(1,1-dimethylethyl)-6-iodophenol hydrochloride (MK-447). This compound was found to be a potent, high-ceiling salidiuretic agent with adjunctive antihypertensive and a n t i -inflammatory properties, and i t is currently undergoing c l i n i c a l evaluation. This report i s a preliminary account (1) of the highlights of our research on this new class of saluretic agents.

TABLE I.

Relative Saluretic A c t i v i t i e s Species

Compound

Rat

la Hydrochlorothiazide Furosemide Ethacrynic Acid a

3

(Admin. Route)

(ρ.ο.)

Dog

(i.v.)

3

4

2

2

3

5

0

5

Presented as scores; assay p r o t o c o l s are d e s c r i b e d in the t e x t , and s c o r i n g criteria are presented i n Tables II and III.

0-8412-0464-0/78/47-083-093$08.25/0 © American Chemical Society Cragoe; Diuretic Agents ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

DIURETIC

94

AGENTS


SALIDIURETIC ACTIVITY ASSAYS The structure-activity relationships (vide infra) in this study were determined by evaluating each synthetic compound for salidiuretic activity i n two animal species, the rat and the dog. A brief description of each assay protocol is given below along with the system used to score the biological results. Oral Rat Assay - Female rats (Charles River, 150-170 g), housed in metabolism cages in groups of three rats per cage, were maintained overnight on a sugar diet with water ad libitum. At the time of the test, each animal was given the test compound orally either as a solution or suspension in 5 ml of water. Urine was collected over the 0-5 hr interval in graduated cylinders and subsequently analyzed for sodium, potassium and chloride content by standard methodology. The saluretic response was scored from 0 to 6 according to the natriuretic c r i t e r i a indicated in Table I I . TABLE I I .

Scoring System f o r O r a l Rat Assay +

yEq Na /cage, dose i n mg/kg Score

1

5

50

81

0.3

0.3

0.4

0.7

0.9 1.5

16.5

0

+ 1

0.3

0.5

1.2

2

0.4

0.6

1.8

2.4

3

0.5

1.4

2.4

2.9

4

1.4

2.7

3.3

5

0.7

2.6

3.3

3.6

6

2.1

3.6

4.2

3.9

Intravenous Dog Assay - Conditioned female mongrel dogs, weighing approximately 20 kg i n the postabsorptive s t a t e , were starved overnight and then given 500 ml o f water o r a l l y 1 h r before i n d u c t i o n o f a n e s t h e s i a with sodium p e n t o b a r b i t a l (30 mg/kg, i . v . ) . A f t e r inducing anesthesia, each dog was prepared with an i n d w e l l i n g bladder c a t h e t e r and primed with c r e a t i n i n e Ο g as a 10% s o l u t i o n i n water) administered s.c. i n m u l t i p l e i n j e c t i o n s i t e s . To ensure uniform hydration and u r i n e pro duction, 1.5 ml/kg o f an isoosmotic pH 7·4 phosphate b u f f e r s o l u t i o n (20 mg phosphate/kg) was given i . v . as a priming i n j e c t i o n p r i o r to i n i t i a t i o n o f clearance s t u d i e s and 3 ml/min o f an isoosmotic pH 7 Λ b u f f e r c o n t a i n i n g k% mannitol (6.9 mg phosphate/min) was i n f u s e d during the experiment. A t the s t a r t o f

Cragoe; Diuretic Agents ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

7.

SMITH ET AL. 2~Aminomethylphenols

95


timed c l e a r a n c e s , the u r i n a r y bladder was emptied and r e p l i c a t e 15-min u r i n e c o l l e c t i o n s were made with venous blood samples being drawn at the midpoint o f each p e r i o d . F o l l o w i n g t h i s c o n t r o l phase, the t e s t compound was administered i . v . s t a t ( i . e . , over a 5 min period) a t 5 mg/kg. Urine was c o l l e c t e d over r e p l i c a t e 15 min p e r i o d s f o r 2 hr and subsequently assayed f o r e l e c t r o l y t e content by standard methodology. The average r a t e o f n a t r i u r e s i s determined f o r the two highest consecutive 15 min c o l l e c t i o n periods was used to score the s a l u r e t i c response from 0 to 5 on the b a s i s o f the sodium e x c r e t i o n r a t e s i n d i c a t e d i n Table I I I .

TABLE I I I .

Scoring System f o r Intravenous

yEq Na /min Score

I.V.

Dog

Assay

at 5 mg/kg Stat

0

0-99

+

a c t i v e above 5 mg/kg

1

100-399

2

400-599

3

600-799

4

800-899

5

900

STRUCTURE-ACTIVITY RELATIONSHIPS The i n i t i a l phase o f t h i s i n v e s t i g a t i o n was d i r e c t e d toward determination o f the b i o l o g i c a l consequences r e s u l t i n g from r e o r i e n t a t i o n and s t r u c t u r a l m o d i f i c a t i o n o f the hydroxyl ( p h e n o l i c ) and aminomethyl groups i n compound l a . As i s shown i n Table IV, o r i e n t a t i o n o f these f u n c t i o n a l groups i n e i t h e r a meta (Compound l b ) or para (Compound I c ) r e l a t i o n s h i p with concomitant p o s i t i o n a l interchange o f the aminomethyl moiety with e i t h e r the 3- or 4-chloro s u b s t i t u e n t r e s u l t e d i n a b l a t i o n o f a c t i v i t y . Hence, these r e s u l t s e s t a b l i s h e d the importance o f m a i n t a i n i n g an ortho r e l a t i o n s h i p between the hydroxyl and aminomethyl groups.


DIURETIC AGENTS

TABLE IV.

Orientation Effects

OH


S a l u r e t i c Score

x

Compd. Ia

x

2

CH NH 2

x

3

CI

2

b

CI

CH NH

c

CI

CI

2

2

4

Rat

Dog

CI

3

4

CI

0

0

0

0

CH NH 2

2

The e f f e c t s o f N - s u b s t i t u t i o n on s a l u r e t i c a c t i v i t y were explored next and a r e tabulated f o r a r e p r e s e n t a t i v e s e r i e s o f s t r u c t u r e s i n Table V· As the data i n d i c a t e , a l k y l a t i o n o f the amino group proved t o be detrimental t o a c t i v i t y as d i d a c y l a t i o n , with exception o f N - t r i f l u o r o a c e t y l a t i o n . In the l a t t e r case, the a c t i v i t y e l i c i t e d upon o r a l a d m i n i s t r a t i o n o f compound I l g i n the rat most l i k e l y r e s u l t e d from i t s i n v i v o h y d r o l y s i s t o the a c t i v e precursor, compound l a . Indeed, the observed f a c i l e conversion o f t r i f l u o r o a c e t a m i d e I l g t o amine I a under m i l d h y d r o l y t i c c o n d i t i o n s (e.g., 20°C, pH 8, 30 min) i n v i t r o i s c o n s i s t e n t with t h i s viewpoint. Meadow, e t a l (2, 3) have reported some o f the b i o l o g i c a l a c t i v i t i e s d i s p l a y e d by a s e r i e s o f t e r t i a r y amines o f general formula I I I ; compound I l i a was i d e n t i f i e d as the most a c t i v e d i u r e t i c member o f the s e r i e s . In our l a b o r a t o r i e s , compound 5H I l i a was found to be i n a c t i v e i n both the r a t and dog d i u r e t i c :H N(CH CHR) Y assays under a v a r i e t y o f t e s t conditions. This r e s u l t i s i n t e r e s t i n g i n view o f the a c t i v i t y , a l b e i t weak, d i s p l a y e d by t e r t i a r y amine l i e . A l t e r a t i o n o f the amino I l i a , R=H; Y=0; methyl group, e.g., by a - s u b s t i t u X =CH CH=CH ; t i o n (Compound IVa), homologation (Compound IVb) o r simultaneous X =0CH α-substitution and homologation (Compound I V c ) , l e d t o s u b s t a n t i a l diminution i n a c t i v i t y as demonstrated i n Table V I . Furthermore,

Ο

0

0

0

4

2

2

6

3


SMITH ET AL.

2-Aminomethylphenols

TABLE V


Effects of N-Substitution

(II)

Cl


Compd

R

lia

NHCH

b

N

(

C

Rat

1

3

V 2

N(CH CH ) 0

d

N(CH )CH -I^

e

2

2

2

3

°

2

c

2

NHCHO

+

1

1

1

0

0 0

f

NHC0CH C1

1

g

NHCOCF

3

h

2

3

NHCOCH NH 2

Dog

2

+

1


DIURETIC AGENTS

98

the corresponding s a l i c y l a l c o h o l (Compound IVd), s a l i c y l a l d e h y d e (Compound IVe) and s a l i c y l i c a c i d (Compound I V f ) analogs o f compound I a were devoid o f demonstrable s a l u r e t i c a c t i v i t y . TABLE V I .

E f f e c t s o f Aminomethyl Group A l t e r a t i o n

OH .χ

2


(IV) ^Cl S a l u r e t i c Score

CI

x

Compd.

2

Rat

IVa

CH(CH )NH

b

CH CH NH

c

CH(OH)CH NH

3

2

2

2

Dog

+

2

2

2

1

^1

0

1

d

CH OH 2

0

0

e

CHO

0

0

f

C0 H

0

0

2

To complete the p r e l i m i n a r y SAR s t u d i e s , the e f f e c t s o f hydroxyl group m o d i f i c a t i o n were determined; the r e s u l t s a r e presented i n Table V I I . As the data i n d i c a t e , both O - a l k y l a t i o n (e.g., as i n compounds Va-c) and replacement o f OH by NH r e s u l t e d i n s t r u c t u r e s with marginal s a l u r e t i c a c t i v i t y . These r e s u l t s coupled with those presented p r e v i o u s l y (vide supra) i n d i c a t e d that: (a) the ortho o r i e n t a t i o n o f the hydroxyl and aminomethyl groups ( i . e . , as i n s a l i c y l a m i n e ) should be maintained, and that (b) these two f u n c t i o n a l groups must remain u n s u b s t i t u t e d . Ac c o r d i n g l y , the e f f e c t s o f nuclear s u b s t i t u t i o n , both s i n g u l a r l y and m u l t i p l y , were i n v e s t i g a t e d i n a systematic manner as an approach to improving s a l u r e t i c a c t i v i t y . 2

Data f o r a r e p r e s e n t a t i v e s e r i e s o f monosubstituted s a l i c y 1 amines (Compound VI) bearing s u b s t i t u e n t s i n the 4 - p o s i t i o n are shown i n Table V I I I . Although s a l i c y l a m i n e i t s e l f (Compound IVa) i s devoid o f demonstrable s a l i d i u r e t i c a c t i v i t y , i n t r o d u c t i o n o f a c h l o r o group i n the 4 - p o s i t i o n (Compound VIb) imparts weak s a l u r e t i c p r o p e r t i e s which a r e maintained upon replacement o f the c h l o r o group by lower a l k y l groups up t o and i n c l u d i n g a three carbon s t r a i g h t chain, with or without α-branching. However, i n t r o d u c t i o n o f the η-butyl group i n the 4 - p o s i t i o n i s not t o l erated, s i n c e compound V l f d i d not e x h i b i t demonstrable a c t i v i t y i n e i t h e r the r a t o r the dog assay.



SMITH ET AL. 2-Aminomethylphenols

TABLE V I I E f f e c t s of Phenol Group M o d i f i c a t i o n

Va

OCH

3

±

0

1

0

b

OCH C0 C H

c

OCH C0 H

+

d

NH

±

2

2

2

2

2

2

5

0


DIURETIC AGENTS

100 TABLE V I I I . OH

E f f e c t s of Nuclear

J

è

Monosubstitution

2 (VI)


S a l u r e t i c Score Compd. Via

x

4

Rat

Dog

H

0

0

b

Cl

1

1

c

C H

1

1

2

5

d

C(CH )

e

CH(CH )C H

f

(CH ) CH

3

3

2

1

3

2

3

3

5

1

0

0

0

Appropriate nuclear d i s u b s t i t u t i o n l e d to marked enhancement of s a l u r e t i c a c t i v i t y as i n d i c a t e d by the r e s u l t s tabulated i n Table IX. The d i c h l o r o d e r i v a t i v e s (Compounds VIIa-c) i l l u s t r a t e the importance of the 4,6-çlisubstitution p a t t e r n , i . e . , V H b i s more a c t i v e than the other p o s i t i o n a l isomers. T h i s *observation, coupled with the information gained from the monosubstituted s e r i e s , prompted preparation o f compounds V I I d - i . Replacement o f the 4 - c h l o r o group i n compound V H b with lower a l k y l groups l e d to markedly improved a c t i v i t y which peaked i n potency with the i n t r o d u c t i o n of a 4 - ( l , l - d i m e t h y l e t h y l ) moiety, i . e . , compound Vlli. I n t e r e s t i n g l y , the 6 - c h l o r o , 6-bromo and 6 - i o d o d e r i v a t i v e s ( i . e . , compounds V l l i , V l l k and V I I I , r e s p e c t i v e l y ) e l i c i t marked s a l i d i u r e t i c responses, whereas, the 6 - f l u o r o analog (Compound V I I j ) i s considerably l e s s a c t i v e . As w i l l be discussed subsequently, the pronounced a n t i h y p e r t e n s i v e p r o p e r t i e s o f M K - 4 4 7 (Compound VIII) served to d i s t i n g u i s h i t from a subseries o f nearly equipotent s a l u r e t i c agents which emerged during the course o f t h i s i n v e s t i g a t i o n . F i n a l l y , i t should be noted that compound Vllm, the primary amine analog of compound I l i a (vide supra), d i s p l a y e d good a c t i v i t y i n both r a t s and dogs. The i n f l u e n c e s of nuclear t r i s u b s t i t u t i o n on s a l u r e t i c a c t i v i t y are presented i n Table X f o r a group o f compounds o f the general s t r u c t u r e V I I I . I t i s noteworthy that s h i f t i n g the 3 - c h l o r o s u b s t i t u e n t i n compound Ia to the 5 - p o s i t i o n ( i . e . , to a f f o r d compound V i l l a ) r e s u l t e d i n s l i g h t l y improved a c t i v i t y i n the dog; whereas, movement o f the 6 - c h l o r o group i n Ia to the


7.

SMITH E T AL. 2-Aminomethylphenob

101

TABLE IX

E f f e c t s o f Nuclear D i s u b s t i t u t i o n


2 (VII)


A

Compd

x

x

3

4

X

5

x

6

Rat

Dog

Cl

Cl

H

H

1

1

b

H

Cl

H

Cl

2

+

c

Cl

H

H

Cl

0

1

d

H

CH

3

H

Cl

2

1

e

H

C H

5

H

Cl

4

5

f

H

(CH ) CH

3

H

Cl

4

5

g

H

CH CH(CH )

2

H

Cl

3

2

h

H

CH(CH )C H

5

H

Cl

5

4

i

H

C(CH )

3

H

Cl

6

5

j

H

C(CH )

3

H

F

4

5

k

H

C(CH )

3

H

Br

6

5

H

C(CH )

3

H

I

6

5

H

CH CH=CH

H

0CH

3

2

Vila

a

l m

2

2

2

2

3

3

2

3

3

3

3

2

2

3

Compound V I I I = MK-447


DIURETIC AGENTS

102

5 - p o s i t i o n ( i . e . , to form compound V H I b ) diminished a c t i v i t y i n the dog while m a r g i n a l l y enhancing a c t i v i t y i n the r a t . F u r t h e r more, i n t r o d u c t i o n o f e l e c t r o n donating s u b s t i t u e n t s (e.g., methyl and methoxy groups) i n the 6 - p o s i t i o n , as i n compounds V H I f and V H I g , proved to reduce a c t i v i t y i n both t e s t s p e c i e s .


TABLE X.

E f f e c t s o f Nuclear T r i s u b s t i t u t i o n

(VIII)

S a l u r e t i c Score Compd.

Χ

3

x*

X

5

x

6

Rat

Dog

Ia

Cl

Cl

H

Cl

3

4

Villa

H

Cl

Cl

Cl

4

4

b

Cl

Cl

Cl

H

4

2

c

F

Cl

H

Cl

4

4

d

Cl

Cl

H

CF

3

4

2

H

Cl

3

2

2

1

1

1

1

0

e f

H

° 3

C H

CH

CH

3

3 3

H

H

° 3

g

Cl

Cl

H

0CH

h

OH

Cl

H

Cl

3

F i n a l l y , the data recorded i n Table XI i l l u s t r a t e the e f f e c t s o f nuclear t e t r a s u b s t i t u t i o n on a c t i v i t y . These data r e v e a l s e v e r a l i n t e r e s t i n g SAR trends. F i r s t , although r e p l a c e ment o f the 3- and 5-chloro s u b s t i t u e n t s o f t e t r a c h l o r o d e r i v a t i v e IXa with methyl groups r e s u l t e d i n g r e a t l y enhanced a c t i v i t y i n the dog, most s u r p r i s i n g l y , the interchange o f c h l o r o and methyl s u b s t i t u e n t s ( i . e . , conversion o f Compound IXb t o compound IXc) t o t a l l y a b o l i s h e d a c t i v i t y . These r e s u l t s i n d i c a t e that both s t e r i c and e l e c t r o n i c e f f e c t s c o n t r i b u t e s u b s t a n t i a l l y i n determining the s a l u r e t i c e f f i c a c y o f these s t r u c t u r e s . Reinforcement f o r the importance o f these e f f e c t s i s provided by a c t i v i t y comparisons o f s t r u c t u r e s IXe with I X f and IXg with IXh. Diminution o f a c t i v i t y accompanies replacement



7. SMITH ET AL.

2-Aminomethylphenols

103

of a chloro s u b s t i t u e n t with a methyl group ( e l e c t r o n i c e f f e c t ) i n the f i r s t instance and r e f l e c t s the r a t h e r s t r i n g e n t s t e r i c requirements f o r s u b s t i t u e n t s i n the 3 - p o s i t i o n i n the second i n s t a n c e . Secondly, the r e s u l t s tabulated f o r compounds IXb, I X i and IXk suggest t h a t , whereas the methyl groups i n the 3 - and 5 - p o s i t i o n s can be replaced with methoxy groups with maintenance of a c t i v i t y , t h e i r replacement with ethoxy moieties s u b s t a n t i a l l y reduces a c t i v i t y . The l a t t e r r e s u l t i s i n accord with the s t e r i c r e s t r a i n t s discussed above f o r s u b s t i t u e n t s i n the 3 - p o s i t i o n . Furthermore, i t should be noted that compounds IXg and I X i d i s p l a y s a l u r e t i c a c t i v i t i e s which are e s s e n t i a l l y o f the same magnitude as those o f the 4 - ( l , l - d i m e t h y l e t h y l ) - 6 - h a l o s a l i c y l a m i n e s ( i . e . , V l l i , V l l k and V I I I ) c i t e d e a r l i e r .

TABLE XI. JH

E f f e c t s of Nuclear T e t r a s u b s t i t u t i o n

2

(IX)

x

3

S a l u r e t i c Score Compd. IXa b c

x

3

X

CI CH

CI CI

3

CI

CH

CH

3

e

CH

3

CH

3

f

CH

3

CH

3

g

CH

3

h

C H 2

i

0CH

Br

CH

4

1

CI

4

5 0

3

5

CI

CI

5

2

CH

CH

3

3

1

CI

5

5

CI

1

1 5

3

CI

5

CI

4

C H

3

Dog

0

CI

OCH

Rat

3

5

OC H

6

Br

C

j

3

CH

CI CH

CI

k

x

5

CI

3

d

2

x

4

3

H

2 5

3 0CH

3

CI

5

CI

0CH

3

Br

5

3

CI

OC H

5

CI

3

0

2


DIURETIC AGENTS

104


In summary, these SAR s t u d i e s i n d i c a t e that s a l u r e t i c a c t i v i t y i s e l i c i t e d by 2-aminomethylphenols which a r e a p p r o p r i a t e l y s u b s t i t u t e d with a hydrogen, methyl or methoxy group i n the 3 - p o s i t i o n , a halo or lower a l k y l ( i . e . , < three carbon s t r a i g h t c h a i n , p r e f e r a b l y α-branched) moiety i n the 4 - p o s i t i o n , a hydrogen or lower a J k y l (or alkoxy) s u b s t i t u e n t i n the 5 - p o s i t i o n and a iodo, bromo o r c h l o r o group i n the 6 - p o s i t i o n , the optimal sub s t i t u e n t combinations and p a t t e r n s being determined by the c i t e d SARs. CHEMISTRY The two general s y n t h e t i c routes which were most f r e q u e n t l y used to prepare the s a l i c y l a m i n e d e r i v a t i v e s studied during the course o f t h i s i n v e s t i g a t i o n a r e summarized i n Scheme I . The f i r s t route i n v o l v e s a c i d - c a t a l y z e d nuclear a m i d o a l k y l a t i o n o f an a p p r o p r i a t e l y s u b s t i t u t e d phenol (Compound X) with an N-hydroxymethylamide, RC0NHCH 0H (R=CH , OELC1, CCI-, CF or CgH ), t o g i v e an N - a c y l s a l i c y l a m i n e o f general formula XI. Subsequent hydrol y t i c N-deacylation o f compound XI Jfollowed by halogenation a f f o r d s the t a r g e t product. The second route i n v o l v e s the same steps but i n an a l t e r e d order, i . e . , halogenation o f phenol X t o give an o-halophenol o f general s t r u c t u r e XII followed by amido a l k y l a t i o n and h y d r o l y s i s . I n both sequences, the key amidomethylation step i s accomplished r e a d i l y v i a the Tscherniac-, Einhorn r e a c t i o n ( 4 ) . The choice o f the proper r e a c t i o n sequence, as w e l l as optimum c o n d i t i o n s ( i . e . , RCONHCH^OH, a c i d c a t a l y s t , r e a c t i o n medium, etc.) f o r i n t r o d u c i n g the aminomethyl moiety, i s governed p r i m a r i l y by^the^chemical nature and d i r e c t i n g i n f l u e n c e s o f the s u b s t i t u e n t s Χ , X and X . The importance o f s e l e c t i n g the proper a c i d c a t a l y s t and r e a c t i o n medium to c o n t r o l the a m i d o a l k y l a t i o n step i s demonstrated i n equation 1. 2

OH

3

NHC0CH Cl

CI XIII


o


7. SMITH ET AL. 2-Aminomethylphenoh

Scheme I


105

DIURETIC AGENTS


106

The d e s i r e d amide (Compound XIa) i s formed i n good y i e l d (6070%) when HOAc-H^SO^ (9:1) i s used, whereas, the use o f ^ S O ^ alone leads to extensive diamidomethylation (diamide X I I I ; , even when equimolar q u a n t i t i e s o f phenol Xa and N-hydroxymethylchloroacetamide are employed. A p p l i c a t i o n o f these general s y n t h e t i c routes t o the elabo r a t i o n o f MK-447 (5) from 4-(1,1-dimethylethyl)phenol (Compound Xb) i s shown i n Figure 1. The r e a c t i o n sequence, Xb >XIb > XIV >MK-447, i s the p r e f e r r e d s y n t h e t i c pathway f o r p r e p a r i n g large q u a n t i t i e s o f MK-447 and can be accomplished r o u t i n e l y i n 50% o v e r a l l y i e l d . Since the 6-iodo s u b s t i t u e n t i s introduced under very mild c o n d i t i o n s ( I C I , 0.5N HC1, 20°C) i n the t e r m i n a l step, t h i s sequence i s i d e a l l y s u i t e d f o r the s y n t h e s i s o f I7-MK-447. The a l t e r n a t i v e pathway, Xb >XIIb ( e i t h e r d i r e c t l y or stepwise v i a c h l o r o m e r c u r i a l X l l a ) >MK-447, a l though q u i t e u s e f u l , i s l e s s s a t i s f a c t o r y than the former as discussed below. The intermediate o-iodophenol X l l b i s somewhat deactivated to e l e c t r o p h i l i c s u b s t i t u t i o n r e l a t i v e to phenol Xa and, t h e r e f o r e , X l l b r e q u i r e s more a c i d i c c o n d i t i o n s to f a c i l i t a t e the Tscherniac-Einhorn r e a c t i o n . The stronger a c i d medium i s conducive to d e i o d i n a t i o n and leads to reduced y i e l d s o f MK447. Nevertheless, the a l t e r n a t i v e pathway proved to be the route o f choice f o r e l a b o r a t i n g MK-447 l a b e l e d with a 2 - ^ £7-aminomethyl moiety. In t h i s i n s t a n c e , conversion o f o-iodophenol X l l b to Ζ^Ε?-ΜΚ-447 was achieved i n 35$ o v e r a l l y i e l d u s i n g N-(hydroxyC C^-methylàchloroacetamide which was conveniently generated i n s i t u from /Z _£7-paraformaldehyde and chloroacetamide. 1

MOLECULAR STRUCTURE, METABOLISM AND PHARMACOLOGY OF MK-447 Molecular S t r u c t u r e - As determined by potentiometric t i t r a t i o n i n water, MK-447 e x h i b i t s pKa-j^ 7.25 and p K a 10.75· These pKa values r e f l e c t the amphoteric p r o p e r t i e s o f MK-347 and, when compared with those (pKa, 8.4, 10.5) d i s p l a y e d by 2-aminomethylphenol hydrochloride, they i n d i c a t e that i n t r o d u c t i o n o f the 6-iodo s u b s t i t u e n t enhances the a c i d i t y o f the phenolic hydroxyl group or, viewed from a d i f f e r e n t p e r s p e c t i v e , serves to reduce net molecular b a s i c i t y , i . e . , monodeprotonation occurs a t a lower pH. When p a r t i t i o n e d between 1-octanol and pH 7.4 b u f f e r , MK-447 i s l o c a l i z e d e s s e n t i a l l y q u a n t i t a t i v e l y ( c a . 99$) i n the l i p i d phase. The f r e e base form o f MK-447, r e a d i l y l i b e r a t e d from MK-447 by n e u t r a l i z a t i o n with weak bases such as ammonia and sodium b i c a r bonate, i s very s o l u b l e i n non-polar organic s o l v e n t s and r e l a t i v e l y i n s o l u b l e i n aqueous media. The l i m i t e d water s o l u b i l i t y of MK-447 f r e e base suggests that i t has appreciable z w i t t e r i o n i c character i n water. Indeed, the v a l i d i t y o f t h i s suggestion was confirmed by determining the e f f e c t s o f pH on X f o r MK-447 i n water. The bathochromic s h i f t from 285 to 309 mywhich accompanies phenoxide formation ( i . e . , ArOH >Ar0~) was observed at pH 6. Hence, the observed s o l u b i l i t y c h a r a c t e r i s t i c s o f MK-447 f r e e base 2

2

m a Y


7.

SMITH ET AL. 2-Aminomethylphenob

JH

NHC0CH C1

OH

2

EtOH-conc. HC1 (3:1),

: ( C H

ΝΗ ·Η01 2

Û C(CH )

3>3

3

Xlb


107

3

XIV

C1CH C0NHCH 0H, 2

2

HOAc, H S 0 2

4

ICI, 0.5 N HC1,

(cat.),

r.t. r.t.

OH

H

NH *HC1 2

Ο CCCH ) 3

3

C(CH ) 3

Xb

2

MK-447 HgCOAc) ;

C1CH C0NHCH 0H,

ICI, HOAc,

2

NaCl, H 0

Δ

2

2

2

H0Ac-H S0 2

4

(10:1);

EtOH-conc. HC1 (3:1),

OH ClHgs

ο

I , 2

C(CH ) 3

HOAc

(CH ) 3

3

3

Xllb

Xlla

Figure 1.

Synthetic routes to MK-447


DIURETIC AGENTS

108


r e f l e c t i t s unique a b i l i t y t o a d j u s t molecular p o l a r i t y solvent-dependent manner as i l l u s t r a t e d i n equation 2. process should be q u i t e f a c i l e s i n c e , a p r i o r i , minimal would be r e q u i r e d t o e f f e c t the depicted i n t r a m o l e c u l a r transfer.

in a This energy proton

"Zwitterion" Examination o f the lowest energy ground s t a t e conformation o f compound V l l i , c a l c u l a t e d by the CNDO/2 formalism (6) and pre sented as an ORTEP p r o j e c t i o n (7) i n F i g u r e 2, a f f o r d s a d d i t i o n a l i n s i g h t i n t o the physicochemical p r o p e r t i e s c i t e d above. First, the plane formed by the C1-C6-C1-0-H atom array i s coplanar with the aromatic r i n g and the p h e n o l i c hydrogen atom ( H ) i s hydrogen bonded t o the c h l o r o s u b s t i t u e n t . T h i s r e s u l t i s i n accord with the recent demonstration o f i n t r a m o l e c u l a r hydrogen bonding i n o-halophenols, i n c l u d i n g 2-iodophenols, by Kollman e t a l (8). Furthermore, although the aminomethyl group i s s i t u a t e d sub s t a n t i a l l y out o f the plane o f the r i n g (-9-= 4 5 ° ) , a second i n t r a m o l e c u l a r hydrogen bond e x i s t s between H^ o f the amino group and the p h e n o l i c oxygen atom. The s o l i d s t a t e s t r u c t u r e o f MK-447 f r e e base, determined by the s i n g l e c r y s t a l X-ray c r y s t a l l o g r a p h i c technique, i s i n reasonable agreement with the c a l c u l a t e d grounds t a t e s t r u c t u r e o f compound V l l i . A comparison o f these s t r u c t u r e s , shown by t h e i r superimposition ( i . e . , one over the other) i n F i g u r e 3, i n d i c a t e s t h a t they d i f f e r i n two r e s p e c t s : (a) compound V l l i contains a H . . . C l , whereas, the -OH group i n MK-447 f r e e base i s not i n t r a m o l e c u l a r l y hyxirogen Bonded; i n s t e a d , i t i s d i r e c t e d below and perpendicular to the plane o f the a r o matic r i n g and (b) the s i z e o f the d i h e d r a l angle -Θ-(45° v s . 53°) i s minimally d i f f e r e n t . The f i r s t s t r u c t u r a l d i f f e r e n c e i s somewhat s u r p r i s i n g and may w e l l r e f l e c t the inherent d i f f i c u l t i e s a s s o c i a t e d with a c c u r a t e l y l o c a t i n g a hydrogen atom proximate to an iodo s u b s t i t u e n t by X-ray c r y s t a l l o g r a p h y . The minor d i f ference i n -Θ- could e i t h e r r e f l e c t the c r y s t a l packing f o r c e s i n the s o l i d s t a t e or stem from the well-known overestimation o f a t t r a c t i v e f o r c e s between non-bonded atoms by the CNDO/2 method (£). In any event, the s u b s t i t u t i o n o f iodo and aminomethyl groups v i c i n a l l y to the hydroxyl moiety f a c i l i t a t e s i n t r a m o l e c u l a r hydrogen bonding which, coupled with the presence o f a 4 - ( l , l dimethylethyl) s u b s t i t u e n t , imparts s u b s t a n t i a l l i p o p h i l i c i t y t o MK-447 f r e e base. Likewise, t h i s nuclear s u b s t i t u t i o n p a t t e r n i s &

x



7. SMITH ET AL.

2-Amtnomethylphenols

Figure 2. The lowest energy ground state conformation of compound Vlli, the 6-chloro analog of MK-447 free base. This conformation, presented as an ORTEP projection, was calculated by the CNDO/2 semiempirical technique.

Figure 3. Comparison of the x-ray structure of MK447 free base (dotted lines) with the CNDO/2-calculated lowest energy ground state conformation of 6-chloro analog VIH (solid lines)


109

110

DIURETIC AGENTS


conducive to z w i t t e r i o n formation i n aqueous media and, thereby, s e v e r e l y l i m i t s the s o l u b i l i t y o f MK-447 f r e e base, but not that of the parent h y d r o c h l o r i d e , i n water. Metabolism - S t u d i e s Î10) i n r a t s , dogs and man i n d i c a t e that o r a l l y administered £ C7-MK-447 i s r a p i d l y absorbed, metabolized and excreted. Peak plasma drug l e v e l s were observed w i t h i n 1 t o 2 hr post drug a d m i n i s t r a t i o n i n a l l three species; a t . J h i s time, the parent drug accounted f o r c a . 15% o f the t o t a l C G7-radioa c t i v i t y i n human plasma and cajj,5$ o f that i n r a t and dog plasma. The h a l f - l i f e o f drug-related"~Zr C 7 r a d i o a c t i v i t y i n the plasma was about 7.5 hr i n man and dogs and 1 hr i n r a t s . In each o f these s p e c i e s , the p r i n c i p l e route o f drug e l i m i n a t i o n ( p r i m a r i l y as metabolites XV and XVI, v i d e i n f r a ) was v i a the u r i n e , whereas, the feces c o n s t i t u t e d the minor pathway f o r drug e x c r e t i o n . As depicted i n Scheme I I , MK-447 i s metabolized i n r a t s and dogs almost e x c l u s i v e l y to the corresponding 0 - s u l f a t e e s t e r (Compound XV). The major human metabolite o f MK-447 has been i s o l a t e d and t e n t a t i v e l y assigned s t r u c t u r e XVI, the N-glucuronide d e r i v a t i v e o f MK-447. The minor human metabolite corresponds to 0 - s u l f a t e e s t e r XV. The assignment o f s t r u c t u r e XV t o the major rat and dog metabolite was confirmed by d i r e c t comparison o f the i s o l a t e d metabolite with an authentic sample o f 2-aminomethyl-4-(l,l-dimethylethyl)-6-iodophenyl hydrogen s u l f a t e which was synthesized by the O-jsulf&tion process presented i n Scheme I I . I t should be noted that compound XV d i s p l a y s marked s a l i d i u r e t i c a c t i v i t y i n both r a t s ( s a l u r e t i c score = 3) and dogs ( s a l u r e t i c score = 5 ) . In view o f the data presented i n Table VII (vide supra) f o r O - s u b s t i t u t e d s a l i c y l a m i n e s Va-c, the observed a c t i v i t y a f t e r a d m i n i s t r a t i o n o f 0 - s u l f a t e e s t e r XV suggests that O - d e s u l f a t i o n occurs a t the proper s i t e i n v i v o , l i b e r a t i n g MK-447 i n agreement with the widely-accepted p r i n c i p l e o f microscopic r e v e r s i b i l i t y , a t l e a s t as i t a p p l i e s to enzymatic transformat i o n s . Hence, although u l t i m a t e l y e l i m i n a t e d v i a u r i n a r y and f e c a l e x c r e t i o n , metabolite XV may w e l l serve i n v i v o as both a depot and a pro-drug form o f MK-447. F i n a l l y , i n s p i t e o f i t s s t r u c t u r a l s i m i l a r i t y t o thyroxine, MK-447 does not undergo detectable d e i o d i n a t i o n e i t h e r i n v i t r o o r i n v i v o . Pharmacology (11) - O r a l l y administered i n both normotensive and spontaneously hypertensive r a t s , MK-447 d i s p l a y e d marked s a l u r e t i c and d i u r e t i c e f f e c t s which were-rapid i n onset and r e l a t i v e l y modest i n d u r a t i o n , the major a c t i o n having occurred w i t h i n the f i r s t 5 h r s . A comparison o f the s a l i d i u r e t i c a c t i v i t i e s o f MK-447, furosemide and h y d r o c h l o r o t h i a z i d e i n normotensive r a t s i s presented i n F i g u r e s 4, 5 and 6. F o r those r e n a l parameters measured, t h i s comparison demonstrates that (a) the c e i l i n g e f f e c t s o f MK-447 exceed those o f furosemide and hydrochlorot h i a z i d e and (b) MK-447 i s s i g n i f i c a n t l y more potent than f u r o semide. A p r e c i s e comparison o f the r e l a t i v e potencies o f MK-447


7. SMITH ET AL.

111

2-Aminomethylphenok

Scheme I I


Metabolism of MK-447

Man

C(CH ) 3

3

XVI

MK-447

P y r i d i n e ^ S 0 , < 25°C 3


DIURETIC AGENTS


112

Na+ E x c r e t i o n mEq/cage/5 h r .

MK-447

FUROSEMIDE

0.1

0.3

1.0

3.0

9.0

27.0

81.0

DOSE, mg/kg P.O. Figure 4. Dose-response regression lines for the natriuretic effects of orally-administered MK-447, furosemide, and hydrochlorothiazide in normotensive rats over a five-hr period. The data points are average values determined per cage for six to nine cages (three rats per cage of each drug. The placebo values for the same period were: Na\ 0.28; K\ 0.16; and Cl~, 0.25 mEq/cage, and urine volume, 28 mL/cage.



113


7.

+

K Excretion mEq/cage/5 Hr.

0.1

0.3

1.0

3.0

9.0

27.0

81.0

DOSE, Mg/Kg P.O. Figure 5. Dose—response regression lines for the kaliuretic effects of orally-administered MK-447, furosemide, and hydrochlorothiazide in normotensive rats over a five-hr period. The data points are average values determined per cage for six to nine cages (three rats per cage) at each dose of each drug. The placebo values for the same period were: Ν a", 0.28; K , 0.16; and CI', 0.25 mEq/cage, and urine volume, 28 mL/cage. +


DIURETIC AGENTS


114

Figure 6. Dose-response regression lines for the chloruretic effects of orally-administered MK-447, furosemide, and hydrochlorothiazide in normotensive rats over a five-hr period. The data points are average values determined per cage for six to nine cages (three rats per cage) at each dose of each drug. The placebo values for the same period were: Na\ 0.28; K , 0.16; and CI; 0.25 mEq/cage, and urine volume, 28 mL/cage. +



7.


115

and h y d r o c h l o r o t h i a z i d e i s precluded by the l a c k o f slope p a r a l l e l i s m i n t h e i r dose-response r e g r e s s i o n l i n e s . Evidence that the s a l i d i u r e t i c a c t i v i t y o f MK-447 may r e l a t e t o i t s a b i l i t y t o enhance kidney l e v e l s o f PGE has been provided by Kuehl, e t a l . (12, 13) who showed that t h i s drug has the a b i l i t y t o enhance the s y n t h e s i s o f PGEs i n ram seminal v e s i c u l a r microsomes and i n i n c u b a t i n g kidney s l i c e s . A t y p i c a l experiment demonstrating the a b i l i t y o f MK-447 t o f a c i l i t a t e the conversion o f a r a c h i d o n i c a c i d t o PGE^ i s shown i n F i g u r e 8. The mechanistic d e t a i l s f o r t h i s a c t i o n o f MK-447 have been described (12, 14). Support f o r the concept that the s a l i d i u r e t i c a c t i o n o f MK-447 r e l a t e s t o PG p r o d u c t i o n i s provided by the f i n d i n g that treatment o f r a t s with indomethacin (2 mg/kg p.o.) 1 h r p r i o r t o dosing with MK-447 a f f e c t e d both e l e c t r o l y t e e x c r e t i o n and u r i n e volumes as shown i n Table X I I . T h i s e f f e c t o f indomethacin on the s a l i d i u r e t i c a c t i o n o f MK-447 was dose-dependent, s i n c e pretreatment with a lower dose (1 mg/kg p.o.) o f indomethacin d i d not s i g n i f i c a n t l y a f f e c t the potency o f MK-447. On the other hand, a t a dose o f 4 mg/kg p.o., indomethacin s u b s t a n t i a l l y reduced both the s a l u r e t i c and d i u r e t i c e f f e c t s o f MK-447. Furthermore, indomethacin (4 mg/kg p.o.) alone m a r g i n a l l y reduced r a t u r i n e volumes, which suggests that the observed e f f e c t o f indomethacin pretreatment may be due only p a r t i a l l y t o a s p e c i f i c antagonism o f the d i u r e t i c a c t i o n s o f MK-447. The s a l i d i u r e t i c e f f e c t s o f MK-447, furosemide and hydroc h l o r o t h i a z i d e g i v e n p.o. i n unanesthetized dogs a r e compared i n Table X I I I . At each o f the doses s t u d i e d , MK-447 d i s p l a y e d s a l u r e t i c and d i u r e t i c e f f e c t s g r e a t e r i n magnitude than those o f e i t h e r furosemide o r h y d r o c h l o r o t h i a z i d e . As observed i n r a t s , MK-447 e l i c i t e d s l i g h t l y more c h l o r u r e s i s than n a t r i u r e s i s i n dogs. K a l i u r e s i s was i n c r e a s e d s i g n i f i c a n t l y by each o f the three drugs. I n a n e s t h e t i z e d dogs, d o s e - r e l a t e d i n c r e a s e s i n e l e c t r o l y t e e x c r e t i o n and u r i n a r y volumes r e s u l t e d from MK-447 g i v e n i . v . over the e n t i r e 0.1 t o 25 mg/kg dose range. The Na /K e x c r e t i o n r a t i o approached 14 a t the h i g h e s t dose (25 mg/kg i . v . ) . When evaluated i n spontaneously h y p e r t e n s i v e (SH) r a t s , MK-447 (dose_> 0.312 mg/kg p.o.) e x h i b i t e d a n t i h y p e r t e n s i v e a c t i v i t y . At doses o f 1.25 and 5 mg/kg p.o., the a n t i h y p e r t e n s i v e e f f e c t s o f MK-447 were r a p i d i n onset ( w i t h i n 1 h r ) , pronounced i n potency and prolonged i n d u r a t i o n ( 24 h r ) . I n a d d i t i o n , the a n t i h y p e r t e n s i v e a c t i v i t y o f MK-447 i n SH r a t s was maintained upon repeated o r a l a d m i n i s t r a t i o n a t 0.312 mg/kg as demonstrated i n Table XIV. Under c o n d i t i o n s where MK-447 (0.312 mg/kg p.o.) produced a pronounced a n t i h y p e r t e n s i v e response, furosemide a t 20 mg/kg p.o. e x h i b i t e d no hypotensive effect. Evidence which suggests that the r e n a l p r o s t a g l a n d i n s , i n a d d i t i o n t o t h e i r p o s s i b l e c o n t r i b u t i o n t o the s a l i d i u r e t i c


DIURETIC AGENTS

116

TABLE X I I Antagonism of the S a l u r e t i c and D i u r e t i c E f f e c t s of MK-447 by Indomethacin P r e t r e a t m e n t i n Normotensive Rats 3

b Values , 0-5 Hr P e r i o d


Excretion

Treatment

Dose (mg/kg p.o.) N a

+

(mEq)

K

+

(mEq)

Urine C l " (mEq) V o l (ml)

Placebo

0

0.28

0.16

0.25

28

MK-447

9

2.70

0.77

3.64

44

MK-447

27

3.19

0.88

4.35

47

MK-447

81

3.51

0.99

4.89

47

MK-447 + Indomethacin

9 2

2.52

0.85

3.59

42


27 2

2.97

0.97

4.24

45


81 2

3.25

1.02

4.70

43

Pretreatment 1 h r p r i o r to dosing with MK-447. per cage, 3 r a t s per cage.

Average values


7. SMITH ET AL.

2-Aminomethylphenoh

117

TABLE X I I I


S a l u r e t i c and D i u r e t i c E f f e c t s o f O r a l l y Administered MK-447 (MK), Furosemide (F) and H y d r o c h l o r o t h i a z i d e (HCT) i n Unanesthetized Dogs

a

E x c r e t i o n Values , 0-24 h r . P e r i o d Na

Dose (mg/kg) MK

0.2

10

0.3

16

+

(mEq) F

HCT

MK

+

F

HCT

12

9

7

25

6

5

F

19

HCT

17

12

11

MK

330

8

25

26

46

570

1.8

42

16

52

700

2

50

17

73

890

59

10

10 24

57

26

18

44 10

18

12

375

660

19

5

510

540

38

37

HCT

440

1.3

3

F

15 36

8

Urine V o l (ml)

260

8 11

22

MK

(mEq)

12

15

1

CI

(mEq)

6

0.5 0.6

K

77

725 31

69

800

590

960

31

1035

760

Average values determined per dog f o r 3 to 47 dogs at each dose o f e a c h dru:^. The placebo values f o r the same p e r i o d were: Na , 4.8; Κ , 6.3; and C l " , 6.3 mEq/dog and u r i n e volume, 210 ml/dog. +


DIURETIC

118

AGENTS

TABLE XIV


A n t i h y p e r t e n s i v e A c t i v i t y of MK-447 Administered O r a l l y i n SH Rats of the Wistar-Okamoto S t r a i n

Group No. (No, o f Rats)

1 (17)

Treatment

Saline 2 ml/kg p.o.

Mean A r t e r i a l Pressure (mmHg + S E ) , Hr a f t e r Treatment

Day

a

4

178+4

180+4

174+3

172+3

173+4

171+3

171+3

171+2

170+2

173+2

163+5

166+7

167+7

2

157+7

161+6

156+5

3

157+4

159+3

181+4

1 2

—

3 2 (5)

MK-447

b

12

24

0

1

185+3

A r t e r i a l pressure was recorded i n unanesthetized male r a t s of 290 to 350 g body weight and 30 to 40 weeks age by a digect technique i n v o l v i n g c a n n u l a t i o n of the caudal a r t e r y . MK-447 (0.312 mg/kg) was administered p.o. i n water i n volumes of 2 ml/kg d a i l y f o r 3 days.



7.

SMITH ET AL.

I 0.01

:

119

2-Aminomethylphenoh

ι

1

0.1

10

ι

10.0 00SE MG/KG P.O.

ι

100.0

——I

Figure 7. Dose-response regression lines for the effects of MK-447 on the mean arterial pressure and Na excretion in spontaneously hypertensive rats. The data points for decreases in mean arterial pressure are average values per rat for four to six rats per dose; the data points for Na+ excretion are average values per cage determined for nine cages (three rats per cage) at each dose. +

20

30 40 X I0" M ( Arochidonic Acid ) 5

Figure 8. The stimuhtory effects of MK447 on the biosynthesis of PGE in ram seminal vesicular microsomes as a func tion of substrate concentration


2


120

DIURETIC AGENTS

e f f e c t s o f MK-447 (vide s u p r a ) . may a l s o play a r o l e i n mediating the a n t i h y p e r t e n s i v e a c t i v i t y o f MK-447 emerged from s t u d i e s i n SH r a t s . In t h i s t e s t s p e c i e s , the marked a n t i h y p e r t e n s i v e e f f e c t s e l i c i t e d by 0.078, 0.312 and 1.25 mg/kg p.o. doses o f MK-447 were s e r i o u s l y attenuated by the o r a l c o a d m i n i s t r a t i o n of e i t h e r indomethacin (1.25 mg/kg) or a s p i r i n (20 mg/kg). I n t e r e s t i n g l y , MK-447 d i s p l a y e d no hypotensive a c t i v i t y i n normotensive Wistar-Kyoto r a t s a t doses up to 20 mg/kg p.o. Of even g r e a t e r pharmacological i n t e r e s t was the observation that MK-447 exhibi t e d a n t i h y p e r t e n s i v e a c t i v i t y i n SH r a t s a t s u b d i u r e t i c doses, i . e . , at doses t e n - f o l d lower than those r e q u i r e d f o r d i u r e s i s as shown by the dose-response r e g r e s s i o n l i n e s i n F i g u r e 7. The r e s u l t s c i t e d above i n d i c a t e t h a t , a t l e a s t i n SH r a t s , the a n t i h y p e r t e n s i v e a c t i v i t y o f MK-447 i s not s o l e l y dependent on i t s d i u r e t i c a c t i v i t y . Further support f o r t h i s view emerges upon examination o f the r e l a t i v e s a l u r e t i c and a n t i h y p e r t e n s i v e a c t i v i t i e s recorded i n Table XV f o r a s e r i e s o f s a l i c y l a m i n e d e r i v a t i v e s . Although compounds IXg, I X i , V l l i , V l l k and MK-447 d i s p l a y n e a r l y equipotent . s a l u r e t i c a c t i v i t i e s i n r a t s and dogs, t h e i r r e l a t i v e a n t i h y p e r t e n s i v e e f f e c t s a r e markedly d i f f e r e n t . Hence, as noted e a r l i e r , the pronounced a n t i h y p e r t e n s i v e propert i e s o f MK-447 served to d i s t i n g u i s h i t from a s u b s e r i e s o f potent s a l i d i u r e t i c agents which emerged from t h i s study. It is i n t e r e s t i n g to note t h a t the i n i t i a l s a l u r e t i c screening l e a d ( l a ) i s not a n t i h y p e r t e n s i v e i n the SH r a t , whereas, the parent s t r u c t u r e , s a l i c y l a m i n e (Compound V i a ) , has demonstrable,, a l b e i t weak, a n t i h y p e r t e n s i v e a c t i v i t y i n the SH r a t , but i t i s devoid of s a l u r e t i c a c t i v i t y . The t h i r d pharmacological a t t r i b u t e of MK-447, a n t i i n f l a m matory a c t i v i t y , was demonstrated by i t s e f f e c t i n reducing both carrageenan-induced f o o t edema i n r a t s and c r o t o n - o i l induced s w e l l i n g i n mouse ears (12, 13)· T h i s a c t i o n was suggested to a r i s e from the a b i l i t y o f MK-447 to scavenge an oxygen centered f r e e - r a d i c a l r e l e a s e d i n the conversion o f PGG^ to PGH^. Evidence has been provided to show that t h i s r a d i c a l i s an important inflammatory mediator (12, 13). The i n i t i a l c l i n i c a l study (15) i n normal v o l u n t e e r s has shown t h a t MK-447 i s a potent, h i g h - c e i l i n g d i u r e t i c i n man as i n d i c a t e d by the n a t r i u r e t i c and k a l i u r e t i c data presented i n F i g u r e 9. In t h i s study, MK-447 d i s p l a y e d marked d o s e - r e l a t e d s a l i u r e s i s and d i u r e s i s with minimal k a l i u r e s i s . Recently, MK-447 was shown to e l i c i t a n t i h y p e r t e n s i v e a c t i v i t y a t d i u r e t i c doses i n man (16). MK-447 i s p r e s e n t l y undergoing f u r t h e r c l i n i c a l i n v e s t i g a t i o n . Whether the a d j u n c t i v e antiinflammatory a c t i v i t y demonstrated f o r MK-447 i n experimental animals w i l l . b e observed i n man i s yet to be e s t a b l i s h e d . Acknowledgments - We a r e indebted to Ms. S. J . deSolms, Mr. A. A. Deana and Mr. N. P. Gould f o r expert s y n t h e t i c a s s i s t a n c e , t o Mr. E. L. Cresson f o r the UV s t u d i e s , to Dr. L. S. Watson (deceased) and to Mr. H. F. Russo f o r the s a l i d i u r e t i c


7. SMITH ET AL.

TABLE XV.

121

R e l a t i v e S a l u r e t i c and A n t i h y p e r t e n s i v e

Structure

S a l u r e t i c Score Rat Dog

Activity

Antihypertensive Score SH Rat RH Dog a


Compd.

2-Aminomethylphenoh

a

R e l a t i v e s c o r e s : outstanding a c t i v i t y = 3; moderate a c t i v i t y = 2; weak a c t i v i t y = 1; i n a c t i v e = 0.


DIURETIC AGENTS

122

Δ Excretion (Drug-Control), mEq/4 Hr.


240h

200h

6.25

12.5

25.0

50.0

100

DOSE, mg, P.O. Figure 9. The natriuretic and kaliuretic effects of orally-administered MK-447 in nor mal human volunteers over a four-hr period. The data points are average values ( Δ excretion = drug control) determined per volunteer in eight volunteers at each dose. Derived from the data of Affrime, M. B., et al. (15).



7. SMITH ET AL. 2-Aminomethylphenols

123

e v a l u a t i o n s , to Dr. A. S c r i a b i n e and to Mr. C . T. Ludden f o r the a n t i h y p e r t e n s i v e s t u d i e s and t o Dr. C. G. Van Arman f o r the antiinflammatory r e s u l t s . G r a t i t u d e i s expressed to Dr. J. L. Humes f o r p r o v i d i n g F i g u r e 8, t o Dr. K. Hoogsteen, Dr. J. Springer and Mr. J. H i r s c h f i e l d f o r the X-ray c r y s t a l l o g r a p h i c a n a l y s i s o f MK-447 f r e e base and t o Dr. G. M. Smith f o r the CNDO/2 modeling s t u d i e s . We wish t o express our a p p r e c i a t i o n to Drs. D. J. Tocco and J. E. Baer and t h e i r colleagues f o r the metabolism s t u d i e s , to Dr. R. 0. Davies, Dr. J. M. Schrogie, Dr. Κ. E. Tempero and Dr. B. L e i f o r the c l i n i c a l i n v e s t i g a t i o n s and to Dr. J. M. Sprague ( r e t i r e d ) , Dr. C. A. Stone and Dr. R. F. Hirschmann f o r t h e i r guidance and encouragement throughout the course o f t h i s i n v e s t i g a t i o n .

Literature Cited and Notes 1. A series of manuscripts describing the details of this investigation is in preparation by Stokker, G. E., Schultz, Ε. Μ., Deana, Α. Α . , deSolms, S. J., Sprague, J. Μ., Smith, R. L . and Cragoe, E. J., Jr., for submission to J. Med. Chem. 2. Meadow, J., Berger, J. and Schert, R., Chim. Therap. (1968), 3, 253. 3. Geschickter, C. and Meadow, J., U.S. Patent 3,080,365 (1968). 4. For an extensive review of the Tscherniac-Einhorn reaction, see Zaugg, H. E. and Martin, W. B. in "Organic Reactions", 14, Adams, R., Blatt, A. H . , Boekelheide, V . , Cairns, T. L., Cope, A. C. and Niemann, C., Eds., J. Wiley and Sons, New York, Ν. Y . , 1965, pp 52-269. 5. Cragoe, E. J., J r . and Schultz, Ε. Μ., U.S. Patent 4,029,816 (1977). 6. Since the Merck Molecular Modeling CNDO/2 program was not parameterized for third and fourth row elements at the time of this study, 6-chloro analog VIIi was subjected to conformational analysis by the CNDO/2 calculational technique; Smith, G. W., unpublished results. 7. Johnson, C. K . , ORTEP, Rep. ORNL-3894 (1965), Oak Ridge National Laboratory, Oak Ridge, Tenn. 8. Dietrich, S. W., Jorgensen, S. W., Kollman, P. A. and Rothenberg, S., J. Am. Chem. Soc. (1976), 98, 8310. 9. Gregory, A. R. and Paddon-Row, M. W., J. Am. Chem. Soc. (1976), 98, 7521. 10. Tocco, D. J., Walker, R. W., Arison, Β. Η., VandenHeuvel, W. J. Α . , Stokker, G. E. and Smith, R. L., for submission to Drug Dispos. Metab. 11. Scriabine, Α . , Watson, L . S., Russo, H. F., Ludden, C. T . , Sweet, C. S., F a n e l l i , G. M . , Jr., Bohidar, N. and Stone, C. Α . , Fed. Proc. (1978), 37, 921. 12. Kuehl, F . Α . , Jr., Humes, J. L., Egan, R. W., Ham, E. Α . , Beveridge, G. C. and Van Arman, C. G . , Nature (1977), 265, 170. 13. Kuehl, F . Α . , Jr., Egan, R. W., Humes, J. L., Beveridge,



124

DIURETIC AGENTS

G. C. and Van Arman, C. G . , in "New Biochemical Aspects of Prostaglandins and Thromboxanes", Fried, J. and Kharasch, N . , Eds., Academic Press, New York, Ν. Y . , 1978. 14. Kuehl, F . Α . , Jr., Oien, H. G. and Ham, E. A. in "Prosta glandins in Cardiovascular and Renal Function", A. Scriabine, F. A. Kuehl, J r . and A. M. Lefer, Eds., Spectrum Publications, New York, 1978, in press. 15. Affrime, M. B., Lowenthal, D. T., Onesti, G . , Busby, P . , Schwartz, C. and L e i , B., C l i n . Pharmacol. Ther. (1977), 21, 97. 16. Davies, R. O., personal communication (to be published). RECEIVED August 21, 1978.


Diuretic Agents - ACS Publications - American Chemical Society

Recommend Documents