1,3-dipolar cycloaddition of (2R,4aR,8aS)-2-phenyl-4,4a-dihydropyrano[3,2-d][1,3]dioxin-6(8aH)-one with aromatic diazomethyl compounds

antonio.manuel.p.ribeiro@gmail.com Small chiral synthons are being more and more appealing to synthetic chemists to build up target molecules possessing multi-stereogenic centres. We have been looking at the usefulness of D-erythrose derivatives obtained from D-glucose. The aldehyde 1[1] was reacted with phosphorane to give ,β-unsaturated compound 2 which was cyclized to lactone 3 in 63.4 % overall yield from 1. The open chain compound 2 resisted to 1,3-dipolar cycloaddition with benzyl azide, but lactone reacted smoothly with benzylazide to afford triazole 4 in 81.3 % yield, with total regioand stereo-selectivity. Diazomethyl compounds have also shown the same trend of excellent selectivities and good yields. All compounds 5 were fully characterized and the stereochemistry studied by n.o.e. experiments.