Cyclopentane-diol

P-D-Gal-O P-Galactosidase Escherichia coli Lactose 4-Cyclopentane-1,4-diol... 

Cyclopentane-diol trans Kieselguhr Methanol-acetone (50 + 50) 0.68 [16]... 

Lipase-catalyzed transesterification of me o-cyclopentane diols 145-149 has been demonstrated by Theil et al. [252] with vinyl acetate as acyl donor and tetrahydrofuran/... 

Figure 52 Lipase-catalyzed transesterification of meso-cyclopentane diols.

Cyclopentene-l-carboxaldehydes are obtained from cyclohexene precursors by the sequence cyclohexene - cyclohexane-1,2-diol -> open-chain dialdehyde - cyclopentane aldol. The main advantage of this ring contraction procedure is, that the regio-and stereoselectivity of the Diels-Alder synthesis of cyclohexene derivatives can be transferred to cyclopentane synthesis (G. Stork, 1953 G. BUchi, 1968). 

A similar rearrangement takes place with A,A-dibenzyl-L-serme benzyl ester [UO (equation 68) and with partially protected carbocyclic nucleosides, such as l-hydroxymethyl-4-(2,4-dinitroanilino)cyclopentane-2,3-diol [133]... 

Incidentally, this represents a better route to 34 (11 %) than that shown in equation 26, since it is not complicated by concurrent formation of 35. The configuration of 34 was confirmed by catalytic hydrogenation, for this afforded a 4-bromo-cyclopentane-l,3-diol that was identical with one of the products of nms-hydroxy-bromination of 3-cyclopentenyl alcohol (Eq. 28). 

Acid-catalyzed hydrolysis of 1,2-epoxy cyclopentane yields a trans-diol, trans-, 2-cyclopentanediol. 

Cyclic compounds also exist in stereoisomeric forms. Let us now study the case of cyclopentane, 1, 2 diol. It has two chiral carbons and exists in three stereoisomeric forms. 

Johnson and Klein (72) prepared the chiral diol (+)-1,2,2-trimethyl-1,3-bis(hydroxymethyl)cyclopentane (50) by the LAH reduction of (+ )-camphoric acid. Consideration of models of the complex of 50 with LAH suggested that... 

For further contributions on the dia-stereoselectivity in electropinacolizations, see Ref. [286-295]. Reduction in DMF at a Fig cathode can lead to improved yield and selectivity upon addition of catalytic amounts of tetraalkylammonium salts to the electrolyte. On the basis of preparative scale electrolyses and cyclic voltammetry for that behavior, a mechanism is proposed that involves an initial reduction of the tetraalkylammonium cation with the participation of the electrode material to form a catalyst that favors le reduction routes [296, 297]. Stoichiometric amounts of ytterbium(II), generated by reduction of Yb(III), support the stereospecific coupling of 1,3-dibenzoylpropane to cis-cyclopentane-l,2-diol. However, Yb(III) remains bounded to the pinacol and cannot be released to act as a catalyst. This leads to a loss of stereoselectivity in the course of the reaction [298]. Also, with the addition of a Ce( IV)-complex the stereochemical course of the reduction can be altered [299]. In a weakly acidic solution, the meso/rac ratio in the EHD (electrohy-drodimerization) of acetophenone could be influenced by ultrasonication [300]. Besides phenyl ketone compounds, examples with other aromatic groups have also been published [294, 295, 301, 302]. 

Cyclohexene TlCl04/HCl04-(Pt) tI(cio4)3 Cyclopentane-1-carboxylic acid, Cyclohexanone, Cyclohexane-1,2-dione, Cyclohexane-1,2-diol 247... 

Bicyclo-[l, 2, 2]-heptane-2,3-diol Cyclopentane-1,3-dicarboxylic acid B [33]... 

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