Cis-2-Cyclopentene-l,4-diol

An application of the meso trick that does not, in principle, require recycling, has been provided (Fig. 7) by a Japanese group (25). Reaction of cis-2-cyclopenten-l,4-diol [36] with W-mesyl-S-phenylalanyl chloride gave, in addition to diester and recovered starting material, the diastereo-meric esters [37] and [38]. Separation was effected by either chromatography or crystallization. Conversion of the free alcohol of [37] to its tetra-hydropyranyl ether and saponification gave alcohol [39], Transfer of the... 

Hydroxylation by hydrogen peroxide in t-butyl alcohol solution is catalyzed by osmium tetroxide. The catalyst is volatile and dangerous to handle but is conveniently used in a solution of the tertiary alcohol. The yields of diols are usually low (30-60%), and the process has not been adapted to large-scale preparations. In contrast to hydroxylation by performic acid, this procedure leads to cis addition of the two hydroxyl groups to the double bond. An extensive study of other catalysts has been made. Some catalysts, e.g., selenium dioxide and pertungstic acid, catalyze addition in the trans direction. Hydroxylation of cyclopentadiene takes place in the 1,4-positions to give 2-cyclopenten-l,4-diol. ... 

Asymmetric Acylation of me o-Diols. Both cyclic and acyclic me o-1,2-diols are desymmetrized by acylation in the presence of a stoichiometric amount of this ligand with modest-to-excellent enantioselectivity (eq 4). In a special case, cis-5,5-dimethyl-2-cyclopentene-l,4-dior was monobenzoylated in the presence of a catalytic amount of this ligand in good yield and with perfect enantioselection (87%, >99.5% ee). 

D. R. Deardorff, C.Q. Windham, C.L. Craney, Enantioselective hydrolysis of as-3,5-diacetox-ycyclopentene (lR,4S)-(+)-4-hydroxy-2-cyclopentenyl acetate - (4-cyclopentene-l,3-diol, monoacetate, (IR-cis)-), Org. Synth. 73 (1996) 25-35. 

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