Trehazolin synthesis cyclization

Uchida and co-workers have further exemplified their synthesis (cf. Vol.28, p.233) of cyclic isoureas, e.g. S a-carbatrehazolin 39, by condensing glycosyl isothiocyanates with the cyclitolamine trehazoline, and cyclizing the resulting thiourea adducts (with HgO) for further details see Chapter 19. cis-Fused 1,2-oxazolidine-2-thiones such as 40 were the exclusive products from reactions of 1,2-O-sulfinyl-a-D-gluco-furanose or -pyranose derivatives (i.e. 1,2-cyclic sulfites) with sodium thiocyanate. ... 

The synthesis of the bromodeoxy and epoxy analogues of trehazoline were achieved by reaction of the aminobromocyclopentitol 280 with glucosyl isothiocyanate 7 to give the thiourea 427 in 50% yield, which underwent cyclization by the action of yellow HgO to afford aminooxazoline 428 in 60% yield. The trans-bxomo-hydrin 428 was stirred in a suspension of potassium carbonate in methanol to form the epoxide 429 in 81% yield (Scheme 60).109... 

Trehazolamine. Chiara has described a synthesis of trehazolamine, the aglycon of trehazolin, a powerful inhibitor of trehalase, wherein a pinacol cyclization provided the necessary cyclopentane framework (Eq. 3.2) [17]. Thus, treatment of the tetrabenzyl-protected keto aldehyde, derived from D-glucose, with Sml2 furnished the two cis diols exclusively as a 1 1 mixture of isomers in excellent yield (>90%) [18]. Previous studies of five-membered ring formation mediated by SmE have also reported good cis/trans selectivity, presumably due to the intervention of a samarium chelate. 

An impressive number of papers has appeared in the past few years based on the use of sugar thioureas as intermediates in the synthesis of the naturally occurring potent trehalase inhibitor trehazolin (251) and of several isomers.52 396-404 The key reaction step involved the cyclization of an A,iV-disubstituted a-D-glucopyranosyl-aminocyclitol (a-D-glucopyranosyl-... 

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