Penicillins absolute configuration

In this context, it should be pointed out that the correlation between aromatic solvent-induced shifts (ASIS) and the axial or equatorial orientation of protons in cyclic sulfoxides and sulfites is quite distinct (211-213) and may be utilized in the assignment of configurations. For instance, the absolute configuration at sulfur was assigned to the penicillin sulfoxide 202 based on analysis of the effect of aromatic solvents on the chemical shifts of protons of the thiazolidine ring (214,215). 

It must be stressed, however, that the methyl alkyl sulfoxide rule is not valid for alkyl benzyl and alkyl allyl sulfoxides (222-224), where the electronic, steric, and solvent effects exert influences on the chiroptical phenomena in a way that is difficult to rationalize. This rule was found to be satisfactory and was used for the assignment of absolute configurations of steroidal (200,201,225), penicillin (226), and amino acid (227-230) sulfoxides. 

Enzymatic treatment with Penicillin G acylase of the phenylacetamide of a RSMA leads to the specific hydrolysis of one enantiomer forming the amine in good yield and high enantiomeric purity (92%).236 Absolute configuration (R) and enantiomeric purity are determined by H1 NMR, after derivatization with (S)-a-trifluoromethylphenylacetic acid (Mosher s salt).302... 

P-Lactam Antibiotics.—The tripeptide [as (159)] isolated from Penicillium chry-sogenum151 has been accepted as a likely key intermediate in the biosynthesis of penicillins with penicillin N (158), the first of the fi -lactams to be formed.152 It has been shown recently that this tripeptide is formed from radio-active L-a-amino-adipic acid, L-valine, and L-cysteine in P. chrysogenum and has the absolute configuration (159).153 Moreover, it has been shown to be a precursor for penicillin... 

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