摘要:
5-O-mesylated furanosides such as 3-dimethylamino-D-xylo (2-beta and 10-beta) or 2-dimethylamino-D-arabino (1-alpha, 7-alpha and 7-beta) readily afford a new class of bicyclic compounds with an azetidinium or a pyrrolidinium ring ; whenever competitive aziridinium ion can be obtained (in the case of 3,5 or 2,5 dimesylates), formation of four or five-membered ring is mainly observed : these ions seem quite unreactive towards fluorinating agents.