Synthesis of phenylalanine-based cyclic acylated enamino ester dipeptide analogues: inhibitors of α-chymotrypsin. X-Ray molecular structure of (2′S,4′R)-4′-benzyl-3′-benzyloxycarbonyl-5′-oxo-2′-phenyloxazolidin-4′-ylacetic acid

Abstract

Alkylation of the (S)-phenylalanine-derived syn-oxazolidinone 8 with BrCH₂CO₂CHPh₂ gave compound 9, a key precursor to the β-keto ester 11 and the keto acid phosphorane 17. Compound 17 gave the enolactone 24 on heating and the bromo enolactones 19 and 20 on treatment with bromine and triethylamine. Compounds 11, 19, 20 and 24 were treated with glycine ethyl ester to give the Phe-Gly dipeptide mimics 22, 23 and 26. The enolactone 24 also gave the Phe-Ala mimic 39 and the Phe-Gly-Gly mimic 34.