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/Et 3 N) 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 (1 R )/(1 S )‐ 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 N 6 ‐benzyladenine gave the two nucleosides 26 and 27 ( Scheme 3 ).