8-Phenylmenthyl Pyruvate

(1R,2S,5R)

[88292-41-5]  · C19H26O3  · 8-Phenylmenthyl Pyruvate  · (MW 302.45) (1S,2R,5R)

[100101-44-8]

(chiral ester for asymmetric induction)

Alternate Name: (1R,2S,5R)-5-methyl-2-(1-methyl-1-phenylethyl)cyclohexyl pyruvate.

Solubility: sol organic solvents.

Form Supplied in: not commercially available.

Preparative Method: isolated as an oil from the acid-catalyzed esterification of (-)-8-Phenylmenthol with pyruvic acid.1

Handling, Storage, and Precautions: susceptible to hydrate formation on exposure to moisture. No other special precautions other than those for combustible organic compounds are necessary.

Chiral a-Hydroxy Acids.

Grignard reagents add to the pyruvate ester of (-)-8-phenylmenthol from the si-face to afford the S-a-hydroxy esters (eq 1).2 Chelation of the pyruvate with magnesium ensures the s-cis conformation and is required for high diastereoselectivity.1 The high degree of diastereoselectivity is attributed to a favorable FMO interaction of the pyruvate with the phenyl moiety.3 The corresponding R-a-hydroxy ester is available by reversing the order of bond formation starting with 8-phenylmenthyl glyoxylate.4

Reduction of 8-phenylmenthyl pyruvate with Potassium Triisopropoxyborohydride in THF gives 90% de of the (R)-lactate ester (eq 2), but other reducing reagents show little selectivity.2 The stereochemical outcome of this reduction is explained as occurring in the s-trans conformation of the pyruvate.

Tin(IV) Chloride-catalyzed ene reaction of the pyruvate ester of (-)-8-phenylmenthol with 1-hexene gives a single diastereomer of the unsaturated (S)-a-hydroxy ester (de > 90%) (eq 3).2 Similarly, tin(IV) chloride-catalyzed ene reactions of 8-phenylmenthyl glyoxylates afford unsaturated secondary alcohols with 93-98% de of the (S) configuration.5


1. (a) Whitesell, J. K.; Bhattacharya, A.; Henke, K. CC 1982, 988. (b) Chen, M.-Y.; Fang, J.-M. JOC 1992, 57, 2937.
2. Whitesell, J. K.; Deyo, D.; Bhattacharya, A. CC 1983, 802.
3. (a) Runsink, J.; Koch, H.; Nehrings, A.; Scharf, H.-D.; Nowack, E.; Hahn, T. JCS(P2) 1988, 49. (b) Whitesell, J. K.; Younathan, J. N.; Hurst, J. R.; Fox, M. A. JOC 1985, 50, 5499.
4. Whitesell, J. K.; Buchanan, C. M. JOC 1986, 51, 5443.
5. Whitesell, J. K.; Bhattacharya, A.; Aguilar, D. A.; Henke, K. CC 1982, 989.

Harry E. Ensley & Shivkumar Mahadevan

Tulane University, New Orleans, LA, USA



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