First asymmetric hetero Diels-Alder reaction of 1-sulfinyl dienes with nitroso derivatives. A new entry to the synthesis of optically pure 1,4-imino-L-ribitol derivatives

Hetero Diels-Alder (HDA) cycloaddition of chiral 1-p-tolylsulfinyl-1,3-pentadiene with benzyl nitrosoformate, under mild conditions, yields 2H-1,2-oxazine 3 with complete regioselectivity and pi-facial diastereoselectivity. Sequential osmylation and protection of the resulting glycol gives the oxazine 5 which is directly transformed into enantiomerically pure 1,4,5-trideoxy-1,4-imino-L-ribitol 8 by reduction under Pd/C.