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 1H- and 13C-NMR chemical shifts, the 1H−H and 13C−1H coupling constants, and the 1H−1H 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.