A new synthetic approach to pseudo-sugars by asymmetric Diels–Alder reaction. Synthesis of optically pure pseudo-β-D-mannopyranose, 1 -amino-1 -deoxypseudo-α-D-mannopyranose and pseudo-α-L-mannopyranose derivatives
Abstract
Synthesis of the optically pure title compounds has been achieved. The key features involved (i) construction of 7-endo-oxabicyclo[2.2.1 ]hept-5-ene-2-carboxylates 3 and 9a by the asymmetric Diels–Alder reaction of (S)s-3-(2-pyridylsulphinyl)acrylate 1 with furans 2 and 8; (ii) stereoselective introduction of a 5,6-exo or -endo diol function to give the protected exo diol 4 and the protected endo diol 10, respectively; (iii) formation of the shikimate derivatives 5 and 11 by cleavage of the oxide bridge of compounds 4 and 10; (iv) conversion of compounds 5 and 11 to the pseudo-sugars 6 and 12, and the pseudo-amino-sugar 7.
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