Dicyclohexyl tartrate

Camphersulfonic add [37], quinine [46], dicyclohexyl tartrate [47], and V-benzoxycarbonylglycyl-L-proline [48]... 

In the kinetic resolution of chiral 1-substituted allylic alcohols, there clearly is benefit to be gained in the choice of tartrate ester used for the reaction. In these reactions, the efficiency of kinetic resolution increases as the size of the tartrate alkyl ester group increases. Data for DMT, DET, and DIPT are summarized below (see Table 6A.8 [6 J), and the trend shown there continues with the use of the crystalline dicyclohexyl and dicyclododecyl tartrates [4],... 

When racemic secondary allylic alcohols 3.17 are subjected to standard Sharpless epoxidation conditions, kinetic resolution takes place [127], By choosing (RJi)- or (5,5)-tartrate, either enantiomer of the epoxyalcohol can be obtained with a maximum yield of 50%, alongside the unreacted allylic alcohol. The ratio of epoxidation rates of the enantiomeric allylic alcohols is usually high enough to obtain both the epoxyalcohol and the unreacted allylic alcohols in high enantiomeric excesses. In some cases, the use of dicyclohexyl- instead of diisopropyl tartrate improves the enantioselectivity. Homoallylic alcohols are also epoxidized, but the selectivities are significantly lower [808]. 

Tartarie acid [(/ ,/ )-20J is one of the most inexpensive chiral compounds available even the (.S. .S )-enantiomer, which does not occur so frequently in nature, is comparatively inexpensive, so there is no need for laboratory synthesis. Most diesters of both enantiomers are also inexpensive, at least for the C, - C3 alcohols. Tartaric acid itself has been used for the chiral modification of the surface of Raney nickel, which permits highly enantioselective reduction of carbonyl groups, e.g., of oxo esters, to the secondary alcohols (Section D.2.3.I.). The zinc salt of tartaric acid has been used for the asymmetric ring opening of epoxides by thiolates (Section C.). The diesters, e.g., 21-25, are conveniently obtained by acid-catalyzed esterification28-31, a method applicable to almost all alcohols as a typical example, dicyclohexyl (f ,tf)-tartrate is given32. 

Openings of mcso-epoxides to obtain chiral P-hydroxy nitrile derivatives and of A -acylaziridines to afford A-(P-sulfenylalkyl) amides have enlisted the service of ligand 23 and dicyclohexyl L-(+)-tartrate, respectively. An efficient method for acquiring chiral azido silyl ethers from epoxides and Me SiN, employs a (salenlCr-N, complex 24. "... 

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