Regioselective synthesis of methyl 5-(N-Boc-cycloaminyl)-1,2-oxazole-4-carboxylates as new amino acid-like building blocks

Abstract

A convenient and efficient synthesis of novel achiral and chiral heterocyclic amino acid-like building blocks was developed. Regioisomeric methyl 5-(N-Boc-cycloaminyl)-1,2-oxazole-4-carboxylates were prepared by the reaction of β-enamino ketoesters (including azetidine, pyrrolidine or piperidine enamines) with hydroxylamine hydrochloride. Unambiguous structural assignments were based on chiral HPLC analysis, 1H, 13C, and 15N NMR spectroscopy, HRMS, and single-crystal X-ray diffraction data.

Keywords

• β-enamino ketoesters
• heterocyclic amino acids
• 15n-labeled 1,2-oxazole
• nmr (1h
• 13c
• 15n)
• 1,2-oxazole (isoxazole)
• x-ray structure analysis