Diastereoselektive Diels‐Alder‐Reaktionen mit α‐Chlornitrososacchariden

Diastereoselective Diels‐Alder Reactions with α‐Chloronitroso Saccharides The α‐chloronitroso reagent 2 obtained from ribose via the lactone oxime 3 reacts with the dienes 6–10 at low temperature to give the chiral dihydrooxazines 11–16 in 63–96% yield and > 96% enantiomeric excess. The reagents 1 and 2 which are approximately mirror images in the vicinity of the chloronitroso function lead to opposite enantiomers of 11–16. The absolute configuration of the products was determined by chemical degradation and comparison with authentic amino and hydroxy acids.