Synthesis Of Phenylpropanoid Glycosides

Carbohydrates play important roles in many biological processes, such as cell-to-cell recognition and interaction, signal transduction, and attachment of pathogen to host cells. Phenylpropanoid glycosides are natural glycosides, many of which possessing potent biological activities such as antiviru, antitumor, antifungal activities and so on. In this dissertation, we studied the synthesis of 3,6-branched phenylpropanoid glycosides as well as related methodologies.1. Synthesis of 3,6-branched trisaccharide phenylpropanoid glycosides, Arenarioside analog (I) and Poliumoside analog (II). Benzyl-protected target molecules, (4-O-benzylphenethyl)-3-O-a-L-rhamnopyranosyl-4-O-(3,4-di-O-benzylcaffeoyl)-6-O-β-D-xylopyranosyl-P-D-glucopyranoside (2.26) and (4-O-benzylphenethyl)-3-O-α-L-rhamnopyranosyl-4-O-(3,4-di-O-benzylcaffeoyl)-6-O-α-L-rhamnopyran-osyl-β-D-glucopyranoside (2.85), were synthesized from D-glucose as starting material via two routes with 21 to 25 step reactions.2. A two-steps, one-pot methodology for the synthesis of 3,6-branched phenylpropanoid glycosides was developed. Using glycosyl trichloroacetimidates and disccharide thioglycosides as donor, we successfully obtained per-protected poliumoside analog (4-O-benzylphenethyl)-3-O-(2,3,4-tri-O-acetyl-α-L-rhamno-pyranosyl)-4-O-(3,4-di-O-benzylcaffeoyl)-6-O-(2,3,4-tri-O-acetyl-a-L-rhamnopy-anosyl)-β-D-glucopyranoside (2.84) in 23% total yield.3. The related methodologies for the synthesis of 3,6-branched phenylpropanoid glycosides were also investigated. It was found that 4,6-0-benzylidene-β-D-glucopyranosides reacted with glycosyl trichloroacetimidates in the presence of TMSOTf could afford (1 →3)-linked disaccharides in good yields with excellent regioselectivity and stereoselectivity. Furthermore, the reaction condition of the selective removal of acetyl group in the presence of caffeoyl group was optimized. The results showed that acetyl protected groups could be released selectively from 3,6-branched phenylpropanoid glycosides in the presence of caffeoyl group using saturated solution of NH₃ in MeOH at 13°C.