Enantioselective total synthesis of semperoside a.
A versatile and concise strategy has been developed (Scheme 1) for the enantioselective synthesis of semperoside A 1 which is endowed with an unusually glucosylated iridane structure. The crucial step was a Hg(II)-mediated electrophilic heteroatom cyclization of beta-glucoside 4 that readily led to the iridane skeleton while installing the C-2 and C-3 stereocenters with complete stereocontrol. This expeditious route is unprecedented among synthetic approaches to iridoid glycosides and smoothly overcomes the hemiacetals glucosidation issue. The present inaugural total synthesis of semperoside A was achieved in 10 steps and 17% overall yield from the enantiomerically pure lactone 8, thus proving the absolute stereochemistry of 1 unequivocally.
Piccinini
Paolo
P
Dipartimento di Chimica Organica, Università di Pavia, Italy.
Vidari
Giovanni
G
Zanoni
Giuseppe
G
D003500:Cyclization; D031450:Gelsemium; D005947:Glucose / Q000737:chemistry; D006842:Hydrocarbons, Brominated / Q000737:chemistry; D039823:Iridoids / Q000138:chemical synthesis*; D007783:Lactones / Q000737:chemistry; D015394:Molecular Structure; D010084:Oxidation-Reduction; D011714:Pyrans / Q000737:chemistry; D013237:Stereoisomerism
D006842:Hydrocarbons, Brominated; D039823:Iridoids; D007783:Lactones; D011714:Pyrans; C488232:semperoside A; D005947:Glucose