Glycosylidene Carbenes. Part 21. Synthesis of N-tosylglycono-1,4-lactone hydrazones as precursors of glycofuranosylidene carbenes

The N′‐(glycofuranosylidene)toluene‐4‐sulfonohydrazides 5 and 10 (Scheme 1) were prepared in good yields by oxidation (1,3‐dibromo‐5,5‐dimethylhydantoin/Et3N) of the N′‐glycosyltoluene‐4‐sulfonohydrazides 4 and 9, which were obtained from 2,3,5‐tri‐O‐benzyl‐D‐ribose (3) and 2,3,5‐tri‐O‐benzyl‐D‐arabinose (8), respectively, and toluene‐4‐sulfonohydrazide. The analogous naphthalene‐2‐sulfonohydrazides 7 and 12 were similarly prepared from 3 and 8 via 6 and 11. Photolysis in the presence of phenol of the sodium salt 15 (Scheme 2), best generated in situ, yielded the anomeric glycosides 16, some 5, and traces of the glycosides (1R)/(1S)‐17. Photolysis of 15 in THF gave the sulfones α‐D/β‐D‐18. Photolysis of 15 (quartz filter) and dimethyl fumarate led to a single cyclopropane 19, the sulfones α‐D/β‐D‐18, and the N‐(ribofuranosyl)‐N′‐(ribofuranosylidene)toluene‐4‐sulfonohydrazide 20. Similarly, N‐phenylmaleimide afforded the cyclopropanes 21 and 22. Photolysis of the sodium salt of 10 and phenol afforded the anomeric glycosides α‐D/β‐D‐23, the C‐glycoside 24, and the sulfone 25. Photolytic glycosidation of 15 with N6‐benzyladenine gave the two nucleosides 26 and 27 (Scheme 3).