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).