s52
GLAMKOWSKI, GAL,SLETZINGER, PORTER, AND WATSON
Hagedorn and Jensen,13 which was modified for autoanalyzer determination, oral doses of 100 mg/kg did not change rat blood glucose. The 1,2-benzisotkiazole 1,l-dioxide series produced hypotensive activity that increased in potency with continuous administration of each active drug (Figure 1) (Table I). An acute hypotensive activity was pro(13) H. C. Hagedorn and B. N. Jensen, Biochem. Z., 136, 46 (1923).
Vul. 10
duced in anesthetized animal preparations (Figures 4 and 7) ; however, this acute response may not have been the same as the activity with chronic administration (Figures 1-3). The acute and the chronic responses may indeed have been responses from two different mechanisms. The responses observed indicate that I11 probably has a mechanism other than blockade of the central or peripheral nervous systems.
4 New- Class of Potent Decarboxylase Inhibitors. p- (3 Indolyl) -why drazinopropionic Acids
-
EDWARD J. GLAMKOWSKI, GEORGE GAL,NEYER SLETZINGER, Merck Sharp & Dohme Research Laboratories, Division of Merck & Co., Inc., Rahway, New Jersey
CURTC. PORTER, AND L. SHERMAN WATSON Merck Institute for Therapeutic Research, West Point, Pennsylvania Received February 6, 1967 Three P-( 3-indolyl)-~~-hydrazinopr~pionic acids were synthesized and tested for in vitro and in vivo inhibition of DOPA decarboxylasa. All were found to be highly active, and one of them, ~~P-(5-hydroxy-3-indolyl)-cuhydrazinopropionic acid, is among the most potent inhibitors of DOPA decarboxylase known.
SCHEME I The biological activity of a-hydrazino acids has only recently been the subject of investigation in spite of the close structural relationship of this class of compounds to the naturally occurring amino acids. I n 1960, .. H Carmi and co-workers' prepared a large number of aliphatic a-hydrazino acids as potential antimetabolites, 1 especially in cancer therapy. These compounds, however, exhibited only a slight nonreproducible activity in Sarcoma 180 tests.2 On the other hand, it has been found that certain aliphatic and particularly aromatic a-hydrazino acids are inhibitors of DOPA decarboxylase in vivo and in vitro.3 Indeed, DL-a-methyl-a2 hydrazino-3;4-dihydroxyphenylpropionic acid (HMD) exhibited a potency 1000 times that of a-methyldopa, its parent compound, and was the most potent DOPA decarboxylase inhibitor available a t that time.3d H I n addition, H M D inhibited formation of serotonin 3 in the, kidneys of mice given 5-hydro~ytryptophan.3~ These results prompted us to synthesize and screen salt of 3-indolylpyruvic acid hydrazone (2). The hyseveral new a-hydrazino acids in the indole series, drazone moiety was then reduced u i t h sodium amalnamely, ~~-P-(3-indolyl)-a-hydrazinopropionic acid, gam to afford ~~-/3-(3-indolyl)-a-hydrazinopropionic ~~-P-(3-indolyl)-a-methyl-a-hydrazinopropionic acid, acid (3). and ~~-~-(5-hydroxy-3-indolyl)-a-hydrazinopropionic The synthesis of D L - (3-indolyl) ~ - a-met hyl- a-hyacid. drazinopropionic acid (see Scheme 11) required as Chemistry.-The synthesis of ~~-fl-(3-indolyl)-a- starting material 3-indolylacetone (4). This comhydrazinopropionic acid (see Scheme I) started with pound was prepared from indole acetic acid via the 3-indolylpyruvic acid (1), prepared according to the acetylative decarboxylation method described by procedure described in a Japanese patent.4 TreatBrown, et aL5 Ketone 4 reacted smoothly with acetic ment of 1 with slightly more than 2 equiv of hydrazine acid hydrazide to give the acetylhydrazone 5. When hydrate resulted in the formation of the hydrazine hydrazine itself was used, the product was found to be a mixture of hydrazone and ketazine. Condensa(1) A. Carmi, G . Pollak, and H. Yellin, J . Org. Chem., 26, 44 (1960). (2) G. Pollak, H. Yellin, and A. Carmi, J . Med. Chem., 1, 220 (1964). tion of intermediate 5 with HCN in DMSO as solvent (3) (a) S.Udenfriend, R.Connamacher, and 9. M. Hem, Biochem. PhaTmagave the a-methyl-a-acetylhydrazinonitrile 6. This col., E,, 419 (1961): (b) 8. Udenfriend and P . Zaltzman-Nirenberg. J . PhaTadduct was then hydrolyzed in two steps. The nitrile nacol. Ezptl. Therap., 138, 194 (1962); ( c ) E. Hansson and W. G. Clark, PTOC. Soc. Ezptl. Bid. Med., 111, 793 (1962); (d) C. C. Porter, L. 9. Watson, group was first transformed to an amide by fortified D. C . Titus, J. A. Totaro, and S. S. Ryer, Biochem. PhaTmacol., 11, 1067 HC1 a t 0". The resulting product was isolated as the (1962); (e) C. R. Creveling, J. W.Dely, and B. W'itkop, J . Med. Chem., 9, 284 (1966). (4) S. Akabori, S. Sakurai, and T. Ito, Japanese Patent 4274 (1959); Chem. A b s t ~ .64, , 13146 (1960).
( 5 ) J. B. Brown, H. B. Henbest, and E. R . H. Jones. J . Chem. Soc., 3172 (1952).
WCH0 SCHEME111
C,,H,CH,O
rhodanme
-.
H
9
/
HCN-DMSO
10
C,,HjCHlO 6
yJ--JCH=1:""
-
H
1. KOH 2. AcOH
NHNHAc
.HC1
+
11
H
7
H 12
H
C,,H,CH,O
HBr
8
H
hydrochloride salt 7. On refluxing 7 in ethanolic KOH 13 overnight, the amide was hydrolyzed to a carboxylic acid arid the acetyl group was removed from the hyBu,N drazino moiety. This gave ~~-P-(3-indolyl)-a-methylNHNH,,HBr a-hydrazinopropionic acid (8). H The final analog in this series, ~~-p-(j-hydroxy-314 indoly1)-a-hydrazinopropionic acid, was prepared as shown in Scheme 111. 5-Benzyloxy-3-indolecarboxaldehyde (9) n as condensed with rhodanine by heating in pyridine solution. Refluxing the resulting rhodanine derivative (10) x i t h aqueous KOH afforded a 63% yield of the desired p-( 5-benzyloxy-3-indolyl)-a-sulfhydrylacrylic acid (11). The starting material, 5benzyloxy-3-indolecarboxaldehyde (9) was also proExperimental Section6 duced in the reaction (3370 yield) but was easily sepaHydrazine Salt of 3-Indolylpyruvic Acid Hydrazone (2).-To a rated from 11. Xext, the a-sulfhydrylacrylic acid stirred mixture of 3-indolylpyruvic acid4 (1, 12.2 g, 0.06 mole) in side chain of 11 was converted to an a-hydrazonoethanol (75 ml) was added slowly 99-1007, hydrazine hi-drate propionic acid moiety by heating in ethanol solution (7.50 g, 0.15 mole). T h e temperature rose from 24 to 30°, and n i t h excess hydrazine. The product 12 was then rewithin a few minutes a clear red solution resulted. The flask was duced to nL-&(3-benzylosy-3-indolgl)-a-hydrazinopro- refrigerated overnight, and t,heri the crystalline product was filtered, washed with cild ethanol, and dried to give 9.70 g (7.28 pionic acid (13) n i t h 3yG sodium amalgam. The reg)' of 2. moval of the benzyl protecting group was accomplished ~~-p-(3-Indolyl)-~~-hydrazinopropionic Acid (3).-To a stirred by treatment n i t h liquid HBr at -73". The resolution of 2 (8.60 g, 0.0345 mole) in water (100 ml) was added 2.3y0 NaHg (200 g), and the system was purged and stirred sulting salt 14, upon addition of tri-n-butylamine to under Nz for 3 days. T h e aqueous phase wasthen separated from pH 5.5, liberated the znitterionic final product, DLthe pool of mercury, extracted once with ether, stirred with ~-(5-hydroxy-3-indolyl)-a-hydrazinopropionic acid (15). charcoal (0.2 g), and filtered. The pH of the filtrate was adjusted The analytical data of these compounds can be found to 5.0 by addition of acetic acid, and the product which precipiin Table I. tated m-as filtered off, washed with xater (three 10-ml portions), and purified as follows. The moist cake was suspended in water Biological Activity.-In Table I1 the new a-hydrazino (50 ml) and 105; HC1 vias added to pH 1.2. The s( liitic,ii A L S acids in the indole series and two highly active conithen charcoaled (0.5 g ) , filtered, and treated with a sodiiim aretile pounds of the DOPA family are compared for their ability to inhibit D O P h decarboxylase in z v b o and (6) Melting points \\ere determined ivith a Thomas-Hoover L-ni-lle:t in I t will be seen that the indole-a-hydrazinc) apparatus in unsealed capillary tubes a n d are uncorrected. Infrared spectra were recorded o n a Perkin-Elmer Model 1 B i Infracord in S u j o l mulls. \\ e acids are all effective inhibitors of DOPA decarboxylase. indebted t o Mr. A. Kalowsky for ultraviolet spectra. and t o hlr. R . N. In p a r t i d a r , u~-p-(5-hydroxy-3-indolyl)-a-hydrazino-are Boos and associates f o r microanalyses. Solvents n e r e concentrated on a found to be almost twice as active rotary evaporator. ,411 prociricts were dr:eu i o r,instant \veirIit i n vnruo uo us nr,-a-hydrazino-a-methyldopa a t 50' unless othernisr stated; in atlditiuri. 1'rOi \ \ a * iiseti t u rLyedite drying thoae solids oirtairied froin n i l i i e o i i s iiirciia. ( 3 l I D ) , and is therefore one of the most potent in( 7 ) \Teiglit yieM of piire p r d u r t aftkr I.r(,t?stalli,.litiun; cf. Table 1 f u r L i L i i (11 of DOI',l decurboxylase known. sol\ C n t used ani: p l i ) weal properties of t l i k analytical >ample.
-
uzzlo.
-
s24
\'(ll.
Compd'
Yield, ,;' Crude Pureb
lip, o c
67
50
.1
-?
69
c
94
1)
34
C
59
D
79
59
C
287-288'
93
74
B
11
176-178'
63
12
200-201'*"
73
D
13
217-2181
77
