Open-chain esters, comparison

No compound other than the methyl ester of N-benzoyl-Lphenylalanine, 33, is an obvious choice for an open-chain analog of the locked substrate 25 but D-24, on the other hand, may be a locked analog of either N-benzoyl-D-alanine methyl ester 34 or of N-formyl-D-phenylalanine methyl ester 35 (75). If 24 is an analog of 34 rather than 35, the comparison of the two locked analogs made in Section V.B. is not valid the phenyl of 24 would then correspond to the benzoyl phenyl of 34. 

Yields, melting points, and specific rotations of nitrodiol monoacetates which were prepared by procedure C described above by using PLE-powder2 instead of purified enzyme. Entries 1 and 3 in Table 1 refer to runs following the above procedure, for all other cases the self made crude PLE-powder was used. The configuration and the sense of chirality of the products of entries 1,3 and 4 were determined by x-ray crystal structure analysis of the camphanic esters, those of the other are inferred by analogy and by NMR comparison. The open chain compounds (entries 1 and 2) were obtained using TES buffer at pH 6.5... 

For lead references see Yamamoto, Y. Maruyama, K. The Opposite Diastereoselectivity in Alkylation and Protonation of Enolates J. Chem. Soc., Chem. Commun. 1984, 904-905. Fleming, I. Lewis, J. J. A Paradigm for Diastereoselectivity in Electrophilic Attack on Trigonal Carbon Adjacent to a Chiral Center The Methylation and Protonation of Some Open-Chain Enolates J. Chem. Soc., Chem. Commun. 1985, 149-151. McGarvey, G. J. Williams, J. M. Stereoelectronic Controlling Features of Allylic Asymmetry. Application to Ester Enolate Alkylations J. Am. Chem. Soc. 1985, 107, 1435-1437. Hart, D. J. Krishnamurthy, R. Investigation of a Model for 1,2-Asymmetric Induction in Reactions of a-Carbalkoxy Radicals A Stereochemical Comparison of Reactions of a-Carbalkoxy Radicals and Ester Enolates J. Ors. Chem. 1993, 57, 4457-4470. 

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