Ethyl N-Boc- and N-Z-α-tosylglycinates were reacted with a variety of aldehydes in the presence of tributylphosphine and a base to afford the corresponding α,β-didehydroamino acid derivatives with high (Z)-selectivity in good yields. Moreover, ethyl (4S)- and (4R)-2-(N-Boc-amino)-4,5-isopropylidenedioxy-2-pentenoates prepared by the present method were converted to (2S, 4S)- and (2R, 4R)-4-hydroxyprolines, respectively.

Reaction of methyl N-Boc-N-phenoxycarbonylglycinate with various aldehydes afforded the corresponding cis-4,5-oxazolidinone derivatives, which were effectively converted to (E)-¡,¢-didehydroamino acids by means of a base. Furthermore, N-deprotection of the oxazolidinone derivatives and subsequent coupling reaction with Boc-amino acid furnished the corresponding dipeptides, which were transformed to dipeptide containing ¡,¢-didehydroamino acid with high E selectivity.

For Abstract see ChemInform Abstract in Full Text.

Amino acids U 0400Stereoselective Syntheses of (E)-α,β-Didehydroamino Acid and Peptide Containing Its Residue Utilizing Oxazolidinone Derivative -(KOMETANI, M.; IHARA, K.; KIMURA, R.; KINOSHITA*, H.; Bull. Chem.

ChemInform Abstract Coupling of 2-oxo-4-phenylbutyric acid (I) with the α-amino esters or amides (II) or (V) is performed in the presence of catecholboranes, yielding the amino acid derivatives (IV) or (VI) mentioned in the title after esterification with diazoethane (III). The preparation of (IV) is optimized using different catecholboranes and varying the solvent and the reaction temperature. The acids derived from the products (VI) are known to be agiotensin converting enzyme inhibitors.