Abstract
With the aim of establishing the structure of the Alangium alkaloid desmethylpsychotrine, stereospecific syntheses of two alternative structures, (±)-9-demethylpsychotrine (1) and (±)-10-demethylpsychotrine (2), have been achieved through a"lactim ether route."The synthesis of (±)-1 started with an initial condensation of the lactim ether 6, derived from the translactam ester 5, with 3-benzyloxy-4-methoxyphenacyl bromide (7a) and proceeded through the intermediates 8a, 9a, 10c, 10a, 11a, 12a, 13a, 14a, and 15a. A parallel sequence of conversions starting with 6 and 4-benzyloxy-3-methoxyphenacyl bromide (7b) produced (±)-2. The 13C nuclear magnetic resonance spectra of (±)-1 and (±)-2 confirmed their endocyclic double bond structure in the dihydroisoquinoline moiety. Spectral comparison of (±)-1 and (±)-2 with natural desmethylpsychotrine suggested formula 1 to be the most likely structure of this alkaloid.
