process for synthesis of a dimer with a indoleinheit and dihydroindoleinheit

摘要

A concerted process for the synthesis of a dimer consisting of an indole unit and a dihydroindole unit possessing natural stereochemistry which comprises:PP(a) forming an N-oxide intermediate from said indole unit;PP(b) treating said N- oxide indole intermediate in the presence of acetic anhydride or halogenated derivative thereof to effect a Polonovski-type fragmentation reaction; PP(c) without isolating the N-oxide indole intermediate and at a temperature of about -10° C. to +10° C., coupling said reaction product with a dihydroindole unit in the presence of acetic anhydride or a halogenated derivative thereof at a low temperature of about -10° C. to +10° C. under inert conditions; and PP(d) subsequently reducing the immonium nitrogen on the indole unit by reacting with aqueous alkali metal borohydride to produce a dimer.