Synthesis of a (2R,6R)-2-(Hydroxymethyl)-6-propa-1,2-dienyl-2H-pyran-3(6H)-one Derivative, a New Enone for the Convergent Construction of C-Glycosides of C-Disaccharides

The previously unknown (2R,6R)-2[(tert-butyl)diphenylsilyloxy]-6-propa-1,2-dienyl-2H-pyran-3(6H)-one (16) was derived from tri-O-acetylglucal. Conjugate addition of PhSAlMe₂ to 16 followed by enolate trapping with 1,2-O-isopropylidene-3-O-methyl-α-d-xylo-pentodialdo-1,4-furanose and NaBH₄ reduction of the intermediate aldol furnished a new C-glycoside of a C-disaccharide: 4,8-anhydro-9-O-[(tert-butyl)diphenylsilyl]-6-[(5R)-1,2-O-isopropylidene-3-O-methyl-α-d-xylo-furanos-5-C-yl]-5-S-phenyl-1,2,3,6-tetradeoxy-5-thio-d-glycero-l-gulo-nona-1,2-dienitol (24). Similarly, conjugate addition of PhMe₂SiZnMe₂Li to 16, followed by cross-aldol reaction with 2,6-anhydro-1,3,4,5-tetra-O-[(tert-butyl)dimethylsilyl]-d-glycero-l-manno-heptose (27), and reduction gave either 4,8-anhydro-6-{(1S)-2,6-anhydro-3,4,5,7-tetra-O-[(tert-butyl)dimethylsilyl]-d-glycero-l-manno-heptitol-1-C-yl}-9-O-[tert-butyl)diphenylsilyl]-1,2,3,5,6-pentadeoxy-5-phenyldimethylsilyl-d-glycero-d-manno-(29) or l-gulo-nona-1,2-dienitol (30).

aldol reaction - carbohydrate-derived enone - conjugate addition - C-disaccharides - C-glycosides - glycal - C-silyl substituted carbohydrate