Hexopyranoses unsaturated, preparation

This process (also known as the Ferrier II Reaction ) has proved to be of considerable value for the efficient, one-step conversion of 5,6-unsaturated hexopyranose derivatives into functionalized cyclohexanones useful for the preparation of such enantiomerically pure compounds as inositols and their amino, deoxy, unsaturated and selectively O-substituted derivatives, notably phosphate esters. In addition, the products of the carbocyclization have been incorporated into many complex compounds of interest in biological and medicinal chemistry. ... 

A convenient approach for the preparation of 3-deoxy-D-xy/o-hexopyranose (27) starts from 1,2 5,6-di-(9-isopropylidene-ot-D-glucofuranose and proceeds via the 3,4-unsaturated derivative 28 (Scheme 15).80... 

In an examination of the stereochemical course of addition of phosphorodithioic acids to 1,2-unsaturated pento- and hexopyranoses, S-deuterated 0,0-dimethyl- and 0,0-bis(2,2-dimethyl-propyl) phosphorodithioates were prepared and reacted with D-glucal. These reactions were found to be fully stereoselective at both reaction centers C-l and C-2 and afforded S-D-ara-binopyranosyl phosphorodithioates 8 and 9 in quantitative yield deuterated at C-2 of the pyranosyl ring14. s... 

Compounds of this class, for example, hexopyranose derivatives having the general formula (123) (see Table II), have most frequently been prepared from the corresponding 6-deoxy-6-iodo or 6-bromo-6-deoxy derivatives of suitably protected aldohexoses or aldohexosides by allowing them to react at room temperature with silver fluoride in pyridine. Alternatively, for example, the 5,6-unsaturated derivative of 1,2 3,4-di-O-iso-propylidene-a-D-galaotopyranose was prepared from the 6-deoxy-6-iodo compound by heating at 130° with sodium methoxide in methanol. Properties of some members of this class are given in Table II. 

A number of -acyl- and thioureido-derivatives of 3 -amino-3 -deoxythymidine have been prepared. 1 0 Michael addition of phthalimide to enal (81) was used in the synthesis of the 3 -amino-2 ,3 -dideoxyhexo-furanose nucleosides (82) (all four isomers, R=H, Me, halogen),191 and a similar enal prepared by mercuric-ion catalysed hydrolysis of L-rhamnal was used in the same way to make the L-acosaminyl nucleoside (83) and its -anomer, and the L-ristosaminyl systems (epimers at C-3 ). 2 Michael addition of 1,2,4-triazole to (81) led, after base-sugar condensation, to the triazolyl-substituted nucleosides (84, B=T, U), together with the analogous hexopyranose systems. 93 xhe imidazolyl nucleosides (85) can be made by reaction of 3 -amino-3 -deoxythymidine with l,4-dinitroimidazoles, 9 whilst the unsaturated imidazole nucleoside (87) was made by treating the phenylselenone (86) (see Section 6) with imidazole. 195... 

The Perrier reaction of 5,6-unsaturated hexopyranoses has been utilised on several occasions for preparing the carbocyclic analogues of lipid ring cleaved analogues, 82 and 83 of lycoricidine and narciclasine alkaloids, and the carba-sugars 84, which are related to allosamizoline. 

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