Synthesis of optically pure 3,4-disubstituted L-glutamates from a novel 2,3-aziridino-gamma-lactone 4-carboxylate derivative

The synthesis of the N-acetyl and N-Cbz derivatives of (1S,4S,5R)-4-(methoxycarbonyl)-3-oxa-6-azabicyclo[3.1.0]hexan-2-one (24 and 27, respectively) from D-ribose is described. While compound 24 reacted with methanol in the presence of boron trifluoride etherate to give the novel 2,3-iminoglutamate derivative 28, compound 27 afforded, under the same conditions, the 4(S)-hydroxy-3(S)methoxy-L-glutamate 31. Similarly, reaction of 27 with ethanol and benzyl alcohol gave the corresponding 3(S)-ethoxy and 3(S)-(benzyloxy) analogues of 31. This represents the first example of the use of a carbohydrate for the preparation of L-glutamate derivatives as well as the first example of a stereocontrolled synthesis of glutamate analogues dissymmetrically substituted at the beta,gamma-positions.