Cyclohexane derivative dihydroxylation

Diels-AUer reactions. This diene can serve as a precursor to the highly oxygenated cyclohexane derivative shikimic acid (3), as shown in Scheme 1. Oxidative desilylation of the Diels-Alder adduct 2 could not be effected with peracids, but was effected by cis-dihydroxylation (Upjohn procedure, 7, 256-257) followed by p-elimination of (CH3)3SiOH with TsOH. Introduction of the 4a,5P diol system was effected indirectly from the 4a,5a-epoxide in several steps, since direct hydrolysis of the epoxide resulted in a mixture of three triols.1... 

A similar cyclisation of an alkene derived from geranyl acetate 24 by dihydroxylation and formation of the epoxide 26 leads to a substituted cyclohexane 28. The Lewis acid ZrCU is used to open the epoxide and the alkene attacks intramolecularly 27 to give eventually the ryn-compound 28 with both substituents equatorial. The alignment of the alkene and the epoxide in a chair conformation 27a is responsible for the diastereoselectivity Note the regioselectivity the less substituted end of the alkene attacks the more substituted end of the epoxide 27. These are just two examples of the very many ordinary ionic reactions that can be used to make six-membered rings. 

A stereoselective [3 + 3] annulalion by a Michael-Wittig reaction on the enal 82 derived from 2,3-0-isopropylidene-(/ )-glyceraldehyde and ethyl-3-oxo-(triphenyl phosphoryU-dene) butanoate (69)" in one pot gave the cyclohexenone derivative 83. Enone reduction and stereoselective dihydroxylation led to formation of highly functionalized cyclohexane systans (85a to 85c) (Schone 22.19). 

The pseudo-sugars 6a-carha-a- (191) and -p-D-fructopyranose (192) have been prepared in six steps from an enzymatically resolved homochiral cyclohexane-triol building block via a common olefinic intermediate 190 by varying the dihydroxylation strategy (osmium tetroxide vs. m-CPBA respectively). Another non-carbohydrate based route to 5a-carba-sugars has been reported which utilizes a 7-norbornanone-derived cyclohexenoid intermediate. The preparation of carba-a- and -p-galacto-, -a-talo- and -a-fucopyranose derivatives were described. ... 

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