Chemoenzymatic Synthesis of Naturally Occurring (Z)-3-Hexenyl 6-O-Glycosyl-β-D-glucopyranosides

Abstract

Direct β-glucosidation between cis-3-hexen-1-ol and D-glucose (5) using the immobilized β-glucosidase from almonds with the synthetic prepolymer ENTP-4000 gave (Z)-3-hexenyl β-D-glucoside (1) in 17% yield.The coupling of the (Z)-3-hexenyl O-β-D-glucopyranoside congener (7) with 2,3,4-tri-O-benzoyl-α-D-xylopyranosyl bromide (8) gave the coupled product (11).Similarly the coupling of 7 with 2,3,4-tri-O-benzoyl-α-L-arabinopyranosyl bromide (9), and that of 7 with 2,3,4-tri-O-benzoyl-α-L-rhamnopyranosyl bromide (10) afforded the coupled products (12 and 13), respectively.Deprotection of the products (11, 12, and 13) afforded (Z)-3-hexenyl O-β-Dxylopyranosyl-(1 → 6)-β-D-glucopyranoside (2), (Z)-3-hexenyl O-α-Larabinopyranosyl-(1→6)-β-D-glucopyranoside (3), and (Z)-3-hexenyl O-α-Lrhamnopyranosyl-(1→6)-β-D-glucopyranoside (4), respectively.(Z)-3-Hexenyl β-D-glucoside (1) is widely distributed in the plant, 1 and was isolated from the leaves of Pertya glabrescens, 1a Epimedium grandiflorum var.thunbergium, 1b the leaves of Celosia argentea, 1f and leaves of Thymus vulgaris.1l Moreover, three kinds of naturally occurring (Z)-3-hexenyl 6-O-glycosyl-β-D-glucopyranoside congeners, (Z)-3-hexenyl O-β-D-xylopyranosyl-(1