First Direct and Detailed Stereochemical Analysis of Strictosidine

Using the easy lactamization of vincoside ( 4 ), epimer-free strictosidine ( 1 ) was prepared from secologanin ( 2 ) and tryptamine ( 3 ). 2D NMR methods were used to determine unambiguously the 1 H- and 13 C-NMR chemical shifts, the 1 H− 1 H and 13 C− 1 H coupling constants, and the 1 H− 1 H NOE interactions in strictosidine ( 1 ). A minimal number of spectroscopic parameters (11 coupling constants, 3 NOEs) and some theoretical considerations have made it possible to select the single species of the 648 selected stereoisomers and to confirm directly the S configuration at the newly formed C-3 chiral center, the P helicity of the dihydropyran and tetrahydropyridine rings, and the conformations around C-14 and the glycosidic bridge.