A new method for the diastereoselective synthesis of alpha-methylpyroglutamates from alpha,beta-didehydro-N-(diphenylmethylene)glutamates has been developed. Deprotection of the (diphenylmethylene) amino moiety of the starting materials affords pyridazinone derivatives which can be transformed into alpha-methyl-6-oxoperhydropyridazine-3-carboxylates in a highly diastereoselective fashion. Ring contraction of the latter induced by LiHMDS affords alpha-methylpyroglutamates. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2002).
Diastereoselective Synthesis and Estimation of the Conformational Flexibility of 6-Oxoperhydropyridazine-3-carboxylic Acid Derivatives
作者:Carlos Alvarez-Ibarra、Aurelio G. Csákÿ、Cristina Gómez de la Oliva
DOI:10.1021/jo0159800
日期:2002.5.1
alpha,beta-Didehydroglutamates have been diastereoselectively transformed into 6-oxoperhydropyridazine-3-carboxylic acid derivatives (OPCAs), which constitute a new class of cyclic amino acid derivatives. Acylation at N-1 renders dipeptides which show considerable conformational rigidity. Semiempirical calculations suggest that OPCAs might force peptide turns with different amplitudes depending on