Efficient removal of N-benzyloxycarbonyl group by a ‘push–pull’ mechanism using thioanisole–trifluoroacetic acid, exemplified by a synthesis of Met-enkephalin
作者:Yoshiaki Kiso、Kazuko Ukawa、Tadashi Akita
DOI:10.1039/c39800000101
日期:——
The N-benzyloxycarbonyl group can be smoothly cleaved undermildconditions, using thioanisole–trifluoroacetic acid, which can deprotect O-benzyltyrosine without the formation of O-to-C rearrangement products; this deblocking method was successfully applied to the synthesis of Met-enkephalin.
Eight Met- and Leu-enkephalin analogs substituted with L- or D-Arg at position 2 were synthesized using NG-mesitylene-2-sulfonylarginine. Among them, H-Tyr-D-Arg-Gly-Phe-Met-OH was found to possess an analgesic effect 2.4 times higher than that of morphine on a molar basis, when injected intracisternally. This compound was also found to produce analgesia when administered intravenously.