Treatment of serine-derived N-(α-haloacetamido)dehydroalanine derivatives with tributyltin hydride in boiling benzene or toluene afforded pyroglutamates in 47–84% yield. The radicalcyclisation reaction, which proceeded regioselectively in a disfavoured 5-endo-trig manner, was found to be most efficient when dichloro- and trichloroamides were employed as starting materials.
Radical reactions leading to substituted pyroglutamates
作者:S. Richard Baker、Andrew F. Parsons、Michelle Wilson
DOI:10.1016/s0040-4039(98)00254-8
日期:1998.4
The Bu3SnH mediated cyclisation of a serine-derived dehydroalanine was shown to provide an efficient approach to a protected 4-phenylpyroglutamate which was elaborated to 4-phenylglutamic acid in good yield. Cyclisation reactions of this type were shown to proceed via an intermediate captodative radical which could be trapped intermolecularly using an alkene e.g. styrene or methyl methacrylate. This