~ I I L I I R E DC. KEBSTWK
'kX00
i C0N:RIBL'TIOEU
PKOM 1HE KEbEARCH
.
Chloramphenicol1 { Chloromycetin)
rJAUORAToRIESOlr PAREL, I ~ A V I S & COMPAVS 1
IX. Some Andogs Having Variations of the Acyl Group
BY MILDRED C. REBSTOCK When the acid was an a-monohalogen subChloramphenicol has been shown to be the dichloroacetamideof D(1evo)-&eo-1-p-nitrophenyl stituted type or halogen substitution WM in some diol.233>4Certain obsewa- position other than a, treatment of the base tions have heen made which suggest that the with the acid chloride in the presence of aqueous amide linkage in chloramphenicol may play a alkali was generally the preferred route of synsignificant role in the biological function of the thesis. In some instances partial esterification compound.6*6 For this reason it was of interest took place when t h i s metbod was used. The to prepare a number of analogs having acyl products of the reaction were then hydrolyzed groups other than the dichloroacetyl group. The under conditions designed to cleave acyloxy present paper deals with the preparation of certain groups without affecting the amide linkage. A amides of DL-and ~-(levo)-threo-l-p-nitrophenyl-2-50% aqueous acetone solution of 0.05 N sodium amino-1,3-propmediol in which the acyl groups hydroxide at 0' served this purpose. This we derived from carboxylic acids. These in- method of hydrolysis waa first used by Kunz and clude amides of normal and branched chain Hudson" for determining the 0-acetyl groups of aliphatic acids (Table I), amides of halogen sub- carbohydrates. stituted aliphatic acids (Table IIa, b and c), The above method of acylation was not pracand amides of certain aromatic acids (Table 111) tical in the preparation of a-bromo or a-iodo acid The availability of these products will now amides in view of the tendency of these compermit studies to be made in which the effect pounds to form morpholoae structures upon of varying the strength of the carbonyl-to- treatment with aqueous alkali. Reaction of the nitrogen linkage in the amide group can be detcr- free base with the a-bromo or a-iodo acid halides mined, as well as the influence of variations in it1 :In inert solvent such as ethyl acetate yielded the remainder of the acyl group. the desired amides. The best yields were obTABLE.
I
0
H
HE SORMAL AND BRANCHED CHAIN ALiPHArICACID AMIDESOF DL- A Y I ) thrCO-l-P-~ITROPHENn-2-AMI~O-~ ,3-PROPANEDIOI, --
-- M p,
O C
166-167 125-126 131-132 108-109 130-131 147-148 127-128 125-126 112-113 129- 130
Mol. n t
C
254.2 254.2 268.2 268.2 382.3 282.3 310.3 296.3 296.3 250.3
51.97 51.97 53.73 53.73 55.31 56.31 58.06 56.74 56.74 55.71
Amides were prepared by a variety of methods, the particular approach depending upon the nature of the acid. When the acid was of the cY,ar-dihalogen or a,a,a-trihalsgen type, the amide was best prepared by treatment of the free base with the methyl or ethyl ester of the acid. (1) Chloramphenicol is the antibiotic drug for which Parke, Davis & Company has adopted the trademark, Chloromycetin.
(2) Rebstock, Crooks, Controutis and Bartz, TIIIS JOURNAL, 71, a448 ~ ~ Q Q o ) . (3) Cantroulis, Rrbstock and Crooks, ibid., 71, 2463 (1949) 14) Long and Troutman, ibid., 71, 2469 (1949) Smith, Worrel and Lilligren, Science, 110, 297 (1949, Smith and Wornel, Arch B w c i t r m , 23, 341 (1949) ~
A n d p e s , '70--Theoretical I1 N
5.62 5.52 6.01 6.01 6.43 6.43 7.14 6.80 6.80 5.76
11.03 11.03 10.4 10.44 9.92 9.92 9.02 9.45 9.45 10.00
SHC!--R I
,:->-C--C--CHrOIf
D-(LE\0/-
--C
52.22 51.98 53.98 53,44 55.05 55.31 58.03 56.98 57.10 55.76
___
Found H
3 57 *i .49 6.25 5.92
OIF -- -
I
II
7
N
Method of prepn
11.26 11.15
I1 I1 I1 11 I1 I1
10.57
6.66 6.63 6.98 6.91 6,66
9.74 10.15 8.80 9.26
9.33
IIIC IIIC IIIC
5.99
10.18
IIIa
tained by carrying out the reaction in an ethyl acetate-water system in the pregence of eufficient sodium bicarbonate to neutralize the acid formed in the reaction. The a,B-dichlwo and cr,P-dibromopropionic tendency to lose acid amides &owed a s-ng hydrogen halide when treated with dilute alkali and it was therefore found preferable to prepare these analogs under aeutral conditions d40. For evidence that the alkali treated products were a,B-unsaturated acid amides, the author is indebted to Dr. J. .If. Vandenbelt of these labora(7) Ruriz and Hudson. THISJ O U R N A L ,48, 1982 (1926).
ACYLGROUPANALOGSOF CHLORAMPHENICOL
Oct., 1950
M. p., 'C.
Mol. wt.
288.7 302.7 316.7 337.1 316.7 357.6 302.7 316.7 337.1 300.7 357.6
99-100 138-139 92-93 119-120 124-125 148-149 155-156 103-104 148-149 122--123 101-102
-
OH
- *Analyses, % *.- -Theoretical C R N 45.76 4.54 9.70 47 61 9.25 4.99 8.84 49.29 5.41 42.75 8.31 4.19 5.41 8.84 49.29 3.10 36.94 7.85 47.61 9.26 4.99 5.41 8.84 49.29 42.75 8 31 4.19 4.36 9.32 47.92 7 86 3.10 36.94 '1
4601
H
'
C
45.74 47.83 49.20 42.90 4g.31 37.17 48.04 49.65
43.M 47.57 37.12
Found H
4.65 5.25 5 40 4.30 5.44 3.43 5.23 5.58 4.33 4.65 3.25
Method oi prem
N
9 45 9.54 8.96 8.50 9.16 7.92 9.11 8.61 8.31
9.32 8.25
IIIC Ilk IIIc
I IIIc I IIlb IIIc IIIa
flIa, IIIc I
TABLE IIb 0
H BROMINE SUBSTITUTED
ACIDAMIDES
-
R
&f P > O C
CH%€k- ( D t ) CH8CHBr-- (DL) CH3CH&HBr- (DL) (CH3)2CBr- (Dt) CH2BrCHBr- (DL) C&=CBr(DL) ClIBr?- (DL) CEJBF~- (D)
130-131 159-160
Mol. wt.
3.33.1 2 361.2 12.3-125 361.2 112-113 426 1 It%-157 126-126 345.1 €+55?-153 4LZ. 1 4i2.1 1m-153
C
39.90 41.51 43.22 43.22 33.$2 41.76 32.06 32.OF
,--
R
M. p., "C.
Mol. wt.
C
Analyses, %Theoretical H N
3.93 4.36 4.75 4.75 3.31 3.80 2.93 2.93
8.41 8.07 7.75 7.75 6.57 8.11 6.80 6.80
AneEpges, % Theorewai H N
OH H
-- _ _ . C
40.08 41.75 43.38 43.39 33.61 41.74 31.94 32.18
C
I 1
--C-CH&%
O F DL AND D-(LEVO)-h'eO-~-NI'l'ROPHENYL-2-
AI(IINO-1,3-PROF'AfiEbK%.
--
I1
NHC-R
Found H
4.25 4.37 5.03 4.94 3.40 3.70 3.10 3.05
F'&W
H
N
8.44 8.30 7.95 7.72' 6.77 8.08
N
Meth6d of prepn.
fIIb IIIb IIIa IIIb 111% EIIa, IIIc I I
Method of prepn.
MILDRED C. REBSTOCK
4802
Vol. 7 2
TABLE111
,
PROPANEDIOL
OII Found €I
I1
N
Method of prepn.
149-161
385 2
49 89
3.66
7.27
49.81
3.88
7.11
IIIc
184-185
409
49.89
5.19
6 81
50 21
4.22
7.07
IIIa
150-151
306.3
54.90
4.61
54.92
4.80
204-205
361.3
53.18
4.18
53.36
4.05
11.78
IIIc
138-139
306.3
5-1.90
4.61
53.15
4.67
9.44
IIIc
11.63
IIIc
tion does involve the formation of a substituted acrylic acid amide and that the remaining chlorine atom is in the a-position. I t may be suggested by analogy that the bromine in the bromoacrylic amide is probably also in the a-position. The amides of aliphatic acids were best prepared by reaction of the base with the acid anhydrides when these were available. Otherwise, the acid chlorides were used in the presence of 800 aqueous alkali. Due t o partial 0-acylation which often occurred under these conditions, selective hydrolysis of the reaction products was usually necessary. With the anhydrides the acylation 600 was more easily controlled and recrystallization of the products yielded the desired amides. Aromatic acid amides were prepared by treat&? ment of the base with the acid chlorides and 400 aqueous alkali. w The foregoing analogs have been tested for antibacterial, antiviral and antifungal properties. The results of these studies will be reported in a 200 subsequent publication. The author wishes to acknowledge her indebtedness to Drs. Leon A. Sweet and George Rieveschl, Jr., for continued interest and en220 260 .300 couragement in this work; to Dr. Harry XI. A, mw Crooks, Jr., for numerous suggestions and advice ; to Dr. J. M. Vandenbelt for the ultraviolet determinations; and to Mr. C. E. Childs and the Misses Geraldine Saladonis and Virginia Pawlik for the many microanalytical determinations. a-bromoacrylic acid amide of ~~-threo-l-p-nitrophenyl-2-
absorption at ca. 245 mp minimum and greater absorption in the region of 215 mp than is observed when the acid amide is saturated. The minimum itself is also shifted from the normal position of 237 mp observed with the saturated amides. The pertinent absorption curves have been plotted in Fig. 1 for reference.
-
amino-1,3-propanediol.
That the chlorine atom remaining in the compound prepared by alkaline treatment of the a,@was in the aby preparing the position was shown a-chloroacrylic acid amide of the DL-tkreo-1-pnitrophenyl-2-amino-1,&propanediol base. Since the compounds were identical this preparation constituted a direct proof that dehydrohalogena-
Experimental Esters (a,a-Dthalogen -Malogen Substituted ethyl estet of the di- or trisubstituted aci The preparation of D-(leVO) t~~o-l-p-nitrop~~l-2-;ti8uoroatetamido - 1,3-propanediol is taken as an example. A mixture of 1.0 g. of D-basela 3 ml. of ethyl difluoroacetate and 10 ml. of absolute (12) D-E- and DL-base refer t o D- and ~ ~ - f h r a o - ~ - n i t r o p h e n y l - 2 amino-l,3-propanediol, respectively
ACYLGROUPANALOGSOF CHLORAMPHENICOL
Oct., 1950
4803
ethanol was refluxed on the steam-bath for 45 minutes. dibromoacetyl chloride was added in portions with vigorThe ethanol was removed a t the water-pump and residue ous stirring during ten minutes. After standing for thirty treated with 30 ml. of low boiling petroleum ether to re- minutes longer the reaction mixture was diluted with 50 The ethyl acetate solution was move excess ester. The petroleum ether was decanted ml. of ethyl acetate. and the residue taken into 200 ml. of ethyl acetate. The washed successively with 0.1 N sulfuric acid and evapoethyl acetate was then washed with 0.1 N sulfuric acid, rated. The residue was crystallized from 20 ml. of ethylene 5% sodium bicarbonate and water., and dried over anhy- dichloride. The crude product melted at 133-1313' and drous magnesium sulfate, and evaporated. The ethyl amounted to 710 mg. The amide was purified to a meltacetate treatment was not absolutely necessary, but gen- ing point of 156-157" by twice recrystallizing from ethyl erally gave a product more easily purified by recrystalliza- acetate, then from ethylene dichloride. When this product or the corresponding a,b-dichlorotion. The residue was taken into 15 ml. of ethylene dichloride from which the product crystallized. A yield of propionic acid amide was treated for one hour at 0' with 1.1 g. of amide melting a t 90-92" was obtained. A 0.05 N sodium hydroxide in 50% aqueous acetone the elesample was recrystallized from ethylene dichloride, ethyl ments of hydrogen bromide or hydrogen chloride were reacetate-low boiling petroleum ether, and finally from moved and the corresponding unsaturated propionic acid amide was obtained. ethylene dichloride to a melting point of 94-96'. IIIb.-A somewhat better yield of the amides was obII. Amide Formation Using Acid Anhydrides.-Anhydrides were preferred as acylation agents to the corre- tained by carrying out the reaction in the presence of sponding acid chlorides. To prepare D-(levo)-threo-1-p- sodium bicarbonate equivalent to the acid halide. A 5-g. nitrophenyl-2-propionamido-l,3-propanediol,a sample of sample of DL-base was suspended in a two-phase system of 1.0 g. of D-base was heated with 3 ml. of propionic an- 25 ml. of distilled water containing 3.96 g. of sodium bihydride on the steam-bath for 20 minutes. Ice-water carbonate (two equivalents) and 100 ml. of ethyl acetate. (50 ml.) was added to the cooled solution to decompose The reaction mixture was cooled to 0" and 4.12 ml. (two the excess propionic anhydride. After one hour the re- equivalents) of bromoacetyl bromide was added in portions action mixture was extracted with three portions of ethyl with vigorous shaking during fifteen minutes. After acetate. The combined extracts were washed succes- standing with intermittent shaking for fifteen minutes sively with 5% sodium bicarbonate: and water, and longer the ethyl acetate layer was separated and the evaporated to a gum. Since partial esterification some- aqueous phase extracted once again. The combined extimes occurs under these conditions, the gum was treated tracts were washed with 0.1 N sulfuric acid, 2% sodium with a mixture of 100 ml. of acetone and 100 ml. of 0.1 N bicarbonate and water, and dried and evaporated. The sodium hydroxide according to the procedure developed product was crystallized from 125 ml. of ethylene dichloby Kunz and Hudson for the selective removal of acyloxy rideoto a yield of 3.25 g. of amide which melted at 129groups? The reaction mixture was kept at 0' for one 130 . II1c.-Excepting the above cases, the most satisfactory hour. Then the solution was neutralized with 5 N sulfuric acid and partially evaporated to remove acetone. method for preparing the amides when the acid chlorides The aqueous residue was made acidic and extracted with were available was to use the acid chloride in the presence two portions of ethyl acetate. The combined extracts of aqueous alkali. To prepare DLJhrro-1-p-nitrophenyl2 g. of DL-base were washed with 0.5% sodium bicarbonate and water and 2-chloroisobutyramide-1,3-propanediol~ dried, and evaporated. The residue was crystallized from was suspended in a two-phase system consisting of 35 ml. 10 ml. of ethylene dichloride. A yield of 700 mg. of prod- of 0.5 N potassium hydroxide and 75 ml. of ethyl acetate The reaction was carried out in a separauct melting at 105-107° was obtained. Recrystallization chilled to 0 from ethylene dichloride, ethyl acetate, and ethylene di- tory funnel which was shaken vigorously throughout. To this system was added 1.5ml. of a-chloroisobutyl chlochloride raised the melting point to 109-110". By heating the base for only ten minutes at 60" with the ride portionwise during ten minutes. The mixture was anhydride, the desired product was obtained without hy- kept alkaline by adding concentrated alkali as needed. drolysis. However, the amides, particularly those of the Fifteen minutes after the final addition the solvents were DL-base, had a tendency to separate before the base had separated. The aqueous layer was extracted once with ethyl acetate. The ethyl acetate extracts were washed completely dissolved and to crystallize on unreacted particles. These impurities could be removed by dis- with 0.1 N sulfuric acid, 5% sodium bicarbonate and water, solving the reaction product in ethyl acetate and washing and dried over anhydrous magnesium sulfate and evaporated. Since some 0-acylation usually occurred during out the unreacted base with 0.1 N sulfuric acid. this treatment the residue was hydrolyzed by treatment IIIa. Amide Formation Using Acid Chlorides.-With the bromo acid halides, monoiodoacetyl chloride and a,p- with cold 0.05 N sodium hydroxide in aqueous acetone.' dihalogen acid chlorides it was preferable to keep the sys- A yield of 2.3 g. of product was obtained when the amide tem neutral. Under alkaline conditions when the mono- was isolated from the hydroiysk mixture and crystallized. bromo or monoiodoacetic acid halides were involved, a The product was p d e d by two recrystallizatiop from secondary reaction occurred in which a morpholone ring ethylene dichloride to a melting point of 123-124 was formed by elimination of hydrogen bromide or hydroSummary gen iodide from the molecule. When a,pdichloro or a,& dibromopropionic acid chlorides were the acylating agents, A number of analogs of chloramphenicol have the products tended to lose hydrogen halide under alkaline been prepared in which substitution of a variety conditions to form a,@-unsaturated acid amides. The of acyl groups for the dichloroacetyl group is preparation of ~~-thrco-l-p-nitrophenyl-2-cu,~~ibromopropionamido-l,3-propanediol is given as an example to made. Amides of normal and branched chain illustrate the conditions which were developed to obtain aliphatic acids, halogen substituted aliphatic these amides without secondary reactions. A sample of acids and aromatic acids are described. 1 g. of DL-base was suspe:ded in 15 ml. of ethyl acetate and MICHIGAN RECEIVED APRIL3, 1950 A volume of 0.5 ml. of a,B- DETROIT, the mixture chilled to 0
.
.
.
