- CaF2 catalyzed SN2 type chlorodehydroxylation of chiral secondary alcohols with thionyl chloride: A practical and convenient approach for the preparation of optically active chloroalkanes
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A CaF2 catalyzed chlorodehydroxylation of chiral secondary alcohols with thionyl chloride has been developed. The chlorination reaction is effective for a wide range of alcohols, generating the corresponding chloroalkanes in good yield with high optical purity with inversion of the original configuration of the alcohol.
- Zhang, Junjie,Wang, Huanxia,Ma, Yun,Wang, Youming,Zhou, Zhenghong,Tang, Chuchi
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p. 2261 - 2263
(2013/05/09)
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- Process for preparing R-(-) -carnitine from S-(-)-chlorosuccinic acid or from a derivative thereof
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An inner salt of L-carnitine is prepared by reduction, with a suitable reducing agent, of a compound of formula (I): where X1and X2, which may be the same or different, are hydroxy, C1-C4alkoxy, phenoxy, halogen, or X1and X2, when taken together are an oxygen atom and the resulting compound is a derivative of succinic anhydride; Y is halogen, the mesyloxy or the tosyloxy group: and subsequent treatment with water, then with a base and then with trimethylamine.
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Page column 11
(2008/06/13)
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- Application of (2)H N.M.R. Spectroscopy to Study the Incorporation of Enantiomeric -Labelled Putrescines into the Pyrrolizidine Alkaloid Retrorsine
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A sample of (2R)-putrescine (13) dihydrochloride was prepared from (2S)-aspartic acid (8), and (2S)-putrescine (15) dihydrochloride was synthesized from (2R)-aspartic acid.Feeding experiments carried out with these precursors on Senecio isatideus plants gave retrorsine (5) containing (2)H, and the distribution of (2)H from each experiment in retrorsine was determined by (2)H n.m.r. spectroscopy.All of the (2)H was confined to the base component of the alkaloid, retronecine (4).Retrorsine (14), derived biosynthetically from (2R)-putrescine (13) dihydrochloride was labelled with (2)H at C-2 and C-6α, while retrorsine (16), produced from (2S)-putrescine (15) dihydrochloride contained (2)H labels at C-6β and C-7α.These labelling patterns demonstrate that hydroxylation at C-7 of retronecine (4) proceeds with retention of configuration.In addition, the formation of the 1,2-double bond of retronecine involves removal of the pro-S hydrogen and retention of the pro-R hydrogen at the carbon atom which becomes C-2 of retronecine.
- Kunec, Ellen K.,Robins, David J.
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p. 1089 - 1094
(2007/10/02)
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