1896
COMMUNICATIONS TO THE EDITOR
Vol. 85
Spackman, Stein and Moorez1 and by microbiological trypsin catalyzed reactions, i.e., preference for the Lassayz2showed an amino acid composition consistent antipode. with the theoretically calculated values (chromatoAn example of diminished stereochemical preference graphic: lYs~.~hisl.ooarg2.~serl.76glu1.~prp1.0~gl~0.~7meto.~~ for the L-antipode in compounds of the type R1’tyro.9gphel.oz; microbiological: lysl,~~his~.o~arg~.~~ser~.~~CONHCHRzCOR3, and associated with the nature proo.?zglyl.~meto.Bs tyr1,04phe~,~). The intact pentadecaof RI’, became available when it was found that the peptide was found to contain tyrosine and tryptophan in kinetic constants for the a-chymotrypsin catalyzed a molar ratio of one to one, as determined spectrophotohydrolysis of N-benzoylalanine methyl ester, in aqueous metrically. solutions a t 25.0°, pH 7.90 and 0.20 M in sodium chloride, were KO = 3.3 f 0.2 m M and ko = 0.0107 f (21) D. H . Spackman. W. H . Stein and S. Moore, A n d . C h c m . , SO, 1190 (1958). 0.0002 set.-' for the D-antipode, and K O = 9.8 =t0.9 ( 2 2 ) The microbiological assay was carried out by the Shankman Laboram M and ko = 0.26 f 0.01 set.-' for the L-antipode.8 tories, Los Angeles, Calif. For N-acetylalanine methyl ester, K O = 611 f 1 0 (23) T . W. Goodwin and R . A. Morton, Biochcm. J . , 40, 628 (1946). m M and ko = 1.29 f 0.02 sec.-l for the L antipode (in (24) This work was supported in part by a grant (GM-2907) from the National Institutes of Health, United States Public Health Service, and a 0.50 M sodium chloride) with no detectable substrate grant from the American Cancer Society. activity being observable for the D-antipode.’O The sought for example of inversion of antipodal HORMONE RESEARCH LABORATORY CHOHHAOLP4 OF CALIFORNIA JANAKIRAMAN RAMACHANDRANspecificity for substrates of the type R1’CONHCHRzUNIVERSITY BERKELEY, CALIFORNIA DAVIDCHUNG COR3 arising from appropriate selection of the group RECEIVED MARCH9, 1963 RI’, with the nature of Rz and R3 remaining invariant, has now been found. In the a-chymotrypsin catalyzed hydrolysis of N-picolinylalanine methyl ester, in A Further Example of Inversion of the Usual Antipodal aqueous solutions a t 25.0°, pH 7.90 and 0.10 M in Specificity of a-Chymotrypsin‘ sodium chloride, values of KO = 18 f 1 m M and ko Sir : = 0.070 0.003 sec.-I were obtained for the L-antipode -15.3 0.3’ (c 3% in water)) (m.p. 59-60’, [aI25~ In 1948 it was shown that the stereochemical course and K O = 17 f 1 m M and ko = 0.165 =t 0.006 set.-' of the papain catalyzed synthesis of a-N-acylated afor the D-antipode (m.p. 59-60’, [alz5”015.3 f 0.3’ amino acid phenylhydrazides, from certain a-N(c 3% in water)). The experiments were conducted with acylated a-amino acids and phenylhydrazine, could be the aid of a pH-statl1sl2 under conditions where [ E ] determined by the structure of the acyl component.2 = 26 p1W3 and [SI = 2.3-18.4 m M for the L-antipode Subsequent s t u d i e ~ confirmed ~?~ and extended these and [E]= 74 p M and [SI = 1.5-12 m M for the Dresults but attempts to observe the same phenomenon antipode. The primary data were evaluated using a with the comparable a-chymotrypsin catalyzed reacDatatron 220 digital computer programmed as detion were U ~ S U C C ~ S S ~ ~ ~ . ~ scribed previously. l 4 In 1960 an inversion of the usual antipodal specificity With three examples of inversion of the usual antiof a-chymotrypsin was demonstrated when i t was podal specificity of a-chymotrypsin, involving both found that the rate of the a-chymotrypsin catalyzed hydrolysis of D-3-carbomethoxydihydroisocarbostyril, conformationally constrained and unconstrained substrates, two of which are a-N-acylated a-amino acid to the corresponding acid, was markedly greater than derivatives, it is evident that substantial support has that of the L-antipode.6 In providing an explanation for the preceding observations a theory was d e v e l ~ p e d ~ . ~now been provided for the explanation of this phenomenon given earlier.7-9 It also follows that the more which not only accounted for the above results but also general t h e ~ r ywhich ~ , ~ envisions non-productive comforecast in general terms the existence of other examples bination of substrate that is fully competitive with its of inversion of antipodal specificity as well as those productive combination with the active site of the involving diminished stereochemical preference in enzyme has acquired added significance. favor of the L-antipode for compounds of the type (10) J . P . Wolf, 111, and C . Niemann, Biochemislry, 2 , 493 (1963). R1’CONHCHR&ORa and cognate structures. (11) T . H . Applewhite, R . B . Martin and C. Niemann, 1.A m . C h c m . Soc., In a recent communication Cohen, et al.,9describe an 80, 1457 (1958). inversion of the usual antipodal specificity in the a(12) T . H . Applewhite, H . Waite and C . Niemann, i b i d . , 80, 1465 (1958). chymotrypsin catalyzed hydrolysis of ethyl a-acetoxy(13) Based upon a molecular weight of 25,000 and a nitrogen content of 16.5%. propionate. This behavior was explained in terms of (14) H . I . Abrash, A. N . Kurtz and C. Niemann, Biochim. B i o p h y s . A d o , a t h e ~ r ywhich ,~ was similar to that developed earlier,’J 46, 378 (1960). and provided a needed example of inversion of antipodal JAMES R. RAPP CONTRIBUTION No. 2948 specificity in a case where the structures were not LABORATORIES OF CHEMISTRY GATESA N D CRELLIN conformationally constrained. However, there reCARLNIEMANN INSTITUTEOF TECHNOLOGY CALIFORNIA mained a need for a demonstration that the nature of PASADENA, CALIFORNIA the group R1’ in compounds of the type RI’CONHCHRECEIVED MARCH18, 1963 RzCOR,, with the nature of R2 and R3 remaining invariant, could determine the degree of stereochemical preference for a given antipode or cause an inversion of Chemistry of Cephalosporin Antibiotics. 111. the antipodal specificity usually observed for a-chymoChemical Correlation of Penicillin and Cephalosporin ( 1 ) Supported in part by a grant from the National Institutes of Health, Antibiotics
*
U S. Public Health Service. ,2) E. L . Bennett and C. Niemann. J . A m . C h c m . Sac., 70, 2610 (1948). (3) (a) H . B. Milne and C. M. Stevens, i b i d . , 72, 1742 (1950); (b) E. L. Bennett and C. Niemann, i b i d . , 73, 1798 (1950). (4) W. H . Schuller and C . Niemann, i b i d . , 79, 1644 (1951). (5) W. H . Schuller and C. Niemann, i b i d . , 74, 4630 (1952). (6) G. E. Hein, R. B. McGriff and C. Niemann, i b i d . , 82, 1830 (1960). (7) G. Hein and C . Niemann, Proc. Nail. A c n d . Sci., 47, 1341 (1961). ( 8 ) G. E. Hein and C. Niemann, J. A m . C h c m . SOL.,94, 4487, 4495
Sir : Recent reports have shown that a series of new, potent, p-lactam-containing antibiotics can be synthesized from the naturally occurring substance, cephalosporin (2.1 These substances have the same carbon skeleton as penicillins but differ by the state of oxida-
(1962). (9) S. G. Cohen. J. Crossley, E. Khedouri and (1962).
(1) (a) B . Loder, G . G . F. Newton and E . P. Abraham, Biochcm. J.. 79, 408 (1961); (b) R. R . Chauvette, e f d ,J . A m . C h c m . SOL.,84, 3401 (1962).
K. Zand, i b i d . , 84, 4163
