Abstract
(3S)-tert-Butyl 2-benzyloxycarbonyl-1, 2, 3, 4-tetrahydro-β-carboline-3-carbamate (III), prepared by the modified Curtius reaction of (3S)-2-benzyloxycarbonyl-1, 2, 3, 4-tetrahydro-β-carboline-3-carboxylic acid (II) with diphenyl phosphorazidate (DPPA) and triethylamine in tert-butyl alcohol, afforded 2-ethyloxycarbonylaminomethyl-3-(2-tert-butyloxy-carbonylamino) ethylindole (Va) by sodium borohydride reduction in ethanol, while reduction in 2-propanol gave the corresponding 2-propyl derivative (Vb) and the compound (VI) containing a novel diazocinoindole skeleton. The mechanism of the reductive cleavage was discussed. Tetrahydropyrrole analog (X) of III and 2-acetyl analog of III afforded the similar ring-cleavage products (XI and XV) by sodium borohydride reduction.
