C/s-Hydroxylation

The Woodward Reaction (or Woodward c/s-Hydroxylation) allows the synthesis of syn-diols from alkenes by the addition of iodine followed by nucleophilic displacement with acetate in the presence of water. Hydrolysis of the intermediate ester gives the desired diol. The Prevost Reaction gives crn/z -diols. 

Periodate compounds have been used for the epoxidation of simple olefins too (MIO4, MH4O6, or M2H3IO6 M = Li, Na, K, Rb, Cs, etc.). In alkaline medium, xenon-trioxide epoxidizes alkenes stereoselectively there is no c/s-hydroxylation as when other inorganic oxides are employed. ... 

The basic cycloadduct, butyl 2-methoxy-5,6-dihydro-2//-pyran-6-carboxylate 2a, can be reduced to 6-hydroxymethyl-2-methoxy-5,6-dihydro-2H-pyran 2b. Both 5,6-dihydro-2ff-pyrans 2a and 2b can be converted in several ways to sugars. c/s-Hydroxylation or epoxidation, followed by basic (or acidic) opening of epoxides with various nucleophilic reagents leads to various 4-deoxyhexoses 3b [18]. Dihydropyran 2b can be transformed in a... 

Oxidation with aqueous permanganate-methylcyclohexane. In an early investigation aimed at elucidating the structure of ergosterol, Reindel and co-workers oxidized ergosterol by an unusual procedure and obtained an oxygenated product which was identified a quarter of a century later in an investigation by M. Fieser, A. Quilico, ct The product proved to be a mixture of about 7 parts of an Oa-compound and 3 parts of an Oj-compound, and the main product was characterized as the triply unsaturated triol (2). It probably arises by c/s-hydroxylation of the 5,6-double... 

Other examples of this novel method of cis-hydroxylation are reported by Cinsburg, Berkley et al., Klass et al. Slates and Wendler, Jefferies and Milligan, and Gunstone and Morris. In the c/s-hydroxylation of d -cholestene the yield of the 2 8-3)3-diol is improved from 50-65% to 81% by carrying out the reaction at 20° under nitrogen for 12 hrs. (standard procedure 45-90° for 1-20 hrs.)... 

This compound, as its 17-ethylene ketal, readily bisdehydrobrominated giving the dienone (136). c/s-Hydroxylation and acetylation gave the 2/S,3)S-diacetate which was further hydroxylated with selenium dioxide to afford the 14a-hydroxy-compound (137) after regeneration of the 17-ketone. Hydrolysis of the acetate functions with base also led to epimerisation and afforded rubrosterone. 

Scheme 10.7 Enantioselective c/s-hydroxylation of a-methylstyrene catalyzed by [OSO4I-BSA complex [33].

The racemic mannonojirimycin derivative 77 was synthesized from furylglycine via the furylamide derivative 75, which formed enone 76 on oxidation (Scheme 21) the cw-2,3-diol was introduced by ruthenium-catalysed c s-hydroxylation of... 

FIGURE 15 Borate ester formation. c/s-Hydroxyls are preferred. The extent of reaction was originaiiy monitored by fbiiowing the change in conductivity of borate soiutions on the addition of saccharide. 

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