Frans-vicinal diols

In the laboratory of S. Kumar, the synthesis of phenolic derivatives of frans-7,8-dihydroxy -7,8-dihydrobenzo[a]pyrene, a highly tumorigenic compound, was accomplished. The frans-vicinal diol functionality was introduced by using the "dry" Prevost conditions. The alkene was subjected to a mixture of iodine and silver benzoate in dry refluxing benzene to give a good yield of the corresponding frans-7,8-dibenzoate derivative. 

G.R. Pettit and co-workers converted a highly substituted frans-stilbene derivative to the strong cancer cell growth inhibitor and antimitotic agent hydroxyphenstatin. The key step of the synthesis was a BFs-OEta-catalyzed pinacol rearrangement of an optically active vicinal diol to afford a substituted diphenylacetaldehyde in racemic form. From this key intermediate, several derivatives were prepared in addition to the target molecule. 

Double bonds can be oxidised to vicinal diols by a variety of reagents of which the most useful are alkaline potassium permanganate and osmium tetroxide. With both reagents, c/s-addition occurs to yield diols of the erythro configuration from c/s-double bonds, and diols of the threo configuration from frans-double bonds. The following procedure utilises alkaline permanganate and is particularly suited to reaction with monoenes and dienes [671],... 

Synthetic polyhydroxy esters have been subjected to GC in the form of the trimethylsilyl ethers [988], as trifluoroacetates [988] and as isopropylidene derivatives [985], Erythro- and fhreo-forms of vicinal diols can be separated on packed columns when they are converted to either of the last two derivatives and, as these compounds can be prepared quantitatively to a high degree of stereochemical purity from cis- or frans-olefins respectively, this provides a basis for gas chromatographic separation and estimation of stereoisomers of unsaturated acids on packed columns [985]. (Epoxide derivatives can be used in a similar manner as discussed in Sections D.1 and 2 above [116,243,244], it appears to be a general rule that derivatives with the trans- or threo-... 

Epoxides are cleaved by treatment with acid just as other ethers are, but under much milder conditions because of ring strain. As we saw in Section 7.8, dilute aqueous acid at room temperature is sufficient to cause the hydrolysis of epoxides to 1,2-diols, also called vicinal glycols. (The word vicimil means "adjacent," and. a glycol is a diol.) The epoxide cleavage takes place by S -like backside attack of a nucleophile on the protonated epoxide, giving a frans-l,2-diol as product. 

Chang, D., Wang, Z., Heringa, M.R, Wirthner, R., Witholt, B. and Li, Z. (2003) Highly enantioselective hydrolysis of alicyclic meso-epoxides with a bacterial epoxide hydrolase from Sphingomonas sp. HXN-200 simple synthesis of alicyclic vicinal frans-diols. Chem. Commun., 960-961. 

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