First total synthesis of two new diglycosides, neohancosides A and B, from Cynanchum hancockianum

Article abstract of DOI:10.1016/S0008-6215(97)00086-4

Neohancosides A (1) and B (2) are monoterpene diglycosides isolated from Cynanchum hancockianum, which is a Chinese folk medicine having antitumor activity. First total synthesis of 1 and 2, (3R)-linaloyl and (3R)-8-hydroxylinaloyl 3-O-β-D-xylopyranosyl-(1 → 6)-β-D-glucopyranosides were achieved stereoselectively using fluoride 12b as a glycosyl donor. The asymmetry of C-3 in 1 and 2 was introduced efficiently by separating diasteremers of (3R), (3S)-linaloyl and (3R), (3S)-8-benzoyloxylinaloyl 3-O-2,3,4-tri-O-benzoyl-β-D-glucopyranoside, 19 and 21 and 20 and 22, respectively. Absolute configurations of 1 and 2 were determined by enzymatic degradation of synthetic intermediates 33 and 34.