Synthesis and photoinitiated thiol-ene reactions ofexo-mannals - a new route toC-β-d-mannosyl derivatives

Syntheses of acyl protectedexo-mannal derivatives were developed starting fromO-peracylated mannopyranosesviathe corresponding anhydro-aldose tosylhydrazones under modified Bamford-Stevens conditions. The synthesis of analogousO-peralkylated (benzylated and isopropylenated) derivatives was carried out from pyranoid and furanoid mannonolactones using methylene transfer reagents. Photoinitiated thiol-ene additions of theseexo-mannals resulted in the correspondingC-(mannopyranosyl/mannofuranosyl)methyl sulfides in medium to good yields with exclusive regio- and beta(d) stereoselectivities.