Preparation and transmetallation of a triphenylstannyl β-D-glucopyranoside: A highly stereoselective route to β-D-C-glycosides via glycosyl dianions

Article abstract of DOI:10.1002/hlca.19940770730

The triphenylstannyl β-D-glucopyranoside 4 was synthesized in one step from the 1,2-anhydro-α-D-glucopyranose 3 with (triphenylstannyl)lithium. Transmetallation of 4 with excess BuLi, followed by quenching the dianion 7 with CD₃OD gave (IS)-1,5-anhydro-3,4,6-tri-o-benzyl-[1-²H]-D-glucitol (8) in 81% yield. Trapping of 7 with benzaldehyde, isobutyraldehyde, or acroleine gave the expected β-D-configurated products 11, 12, and 13 in good yields. Preparation of C-acyl glycosides from acid chlorides, such as acetyl or benzoyl chloride was not practicable, but addition of benzonitrile to 7 yielded 84% of the benzoylated product 14. Treatment of 7 with MeI led to 15 (30%) along with 40% of 18, C-alkylation being accompanied by halogen-metal exchange. Prior addition of lithium 2-thienylcyanocuprate increased the yield of 15 to 50% and using dimethyl sulfate instead of MeI led to 77% of 15. No α-D-anomers could be detected, except with allyl bromide as the electrophile, which yielded in a 1:1 mixture of the anomers 16 and 17.