Iterative benzyne-furan cycloaddition reactions: studies toward the total synthesis of ent-Sch 47554 and ent-Sch 47555.

[reaction: see text] 7-Fluoro-5,8-dimethoxy-1-naphthol, prepared from the lithiation and benzyne formation from 1,4-difluoro-2,5-dimethoxybenzene and Diels-Alder cycloaddition with furan, was sequentially C-glycosidated under Suzuki conditions and O-glycosidated using di-O-acetyl-L-rhamnal to provide the corresponding beta-naphthyl C,O-disaccharide. Further lithiation, benzyne formation, and cycloaddition with furan gave an oxa-bridged 1,4-dihydroanthracenyl C,O-disaccharide, a model compound relevant to the total synthesis of Sch 47555.