Robert W. Weber

Stereospecific synthesis of trans-1,3-disubstituted-1,2,3,4-tetrahydro β-carbolines

Abstract The stereospecific synthesis of trans -1,3-disubstituted-1,2,3,4-tetrahydro β-carbolines has been accomplished in good yield by a two step sequence which involves Pictet-Spengler condensation of N b -benzyltryptophan methyl ester with aldehydes, followed by removal of the 2-benzyl moiety from the corresponding tetrahydro β-carboline via catalytic hydrogenation.

Pictet-spengler reactions in aprotic media. The total synthesis of (±) suaveoline

Abstract The first total synthesis of the indole alkaloid (±)-suaveoline 1 (a macroline-related base and a member of the sarpagine/ajmaline class of alkaloids) was completed in a stereocontrolled fashion. The serial synthesis employed three intramolecular reactions, the Pictet-Spengler cyclization ( 11 → 20 ), the Dieckmann condensation ( 21 → 22 ) and the orthoester Claisen rearrangement ( 25 → 30 ), all of which occurred with high stereoselectivity. Construction of the unique 3,4,5-trisubstituted pyridine ring ( E ) of 1 was executed by addition of hydroxylamine hydrochloride to an ethanolic solution of the corresponding 1,5-daildehyde 36 which was followed by heating. The related base (±)-N b -methylsuaveoline 38 was prepared from 37 via catalytic devenzylation (Pd/C, H 2 ) in the presence of formic acid (78% yield).