Phenylmenthyl Glyoxylate

Hydroperoxide-n-Butyllithium gives 50% de. Chiral 3-amino esters of 8-phenylmenthol have been prepared in 50-60% de by the addition of amines to the re face of 8-phenylmenthyl crotonate under 14-15 kbar pressures (eq 2). Much higher (75 to 99%) de is obtained using 8-0-naphthyl)menthol crotonate. The 3-amino esters obtained are of the proper configuration for conversion to biologically active 3-lactams.  

Meth-Cohn, O. Moore, C. Taljaard, H. C. J. Chem. Soc., Perkin Trans. 

Harry E. Ensley Yunjie Dang Tulane University, New Orleans, LA, USA 

Preparative Methods ozonolysis of 8-Phenylmenthyl Acrylate, NaOAc-catalyzed elimination of nitrite ion from nitrate esters, and direct esterification with glyoxylic acid.  

Ene Reactions. Lewis acid (Tin(IV) Chloride or Titanium(IV) Chloride) catalyzed ene reactions of the glyoxylate esters of 8- 

---

The diastereofacial selective imine-ene reactions with a-imino esters prepared from (—)-8-phenylmenthyl glyoxylate have provided an efficient entry to the asymmetric synthesis of a-amino acids, and a Lewis acid-mediated intramolecular imine-ene reaction has been used for the key spirocyclization step in a recent synthesis of (—)-perhydrohistrionicotoxin. Asymmetric azo-ene reactions have been effected using the chiral azo-enophile, di-(—)-(lR,2S)-2-phenyl-l-cyclohexyldiazenedicarboxylate. ... 

Diastereoselective alkylation of phenols.1 In the presence of TiCl4, phenols react with glyoxylates at -30 to 20° exclusively at the ortlio-position to form 2-hydroxymandelic esters. A substituent has no effect on the site of substitution. Use of a chiral glyoxylate, in particular (- )-8-phenylmenthyl glyoxylate, results in high... 

An excellent simple and induced selectivity could be obtained by Mulzer and his group [92] in the cycloaddition of 2-trimethylsilyl-oxy-l,3-pentadiene 2-31 and (lR,2S,5R)-8-phenylmenthyl glyoxylate 2-32 [93] in the presence of 0.2 equivalents of anhydrous MgBr2 in THF at 0 °C. After acidic workup the ketone 2-33 was isolated as a single diastereomer (>98%), which was then used for synthesis of the C-26-C-32 tetrahydropyran moiety of swinholide. In contrast,... 

Miscellaneous. The acrylate provides a synthon for the preparation of 8-Phenylmenthyl Glyoxylate, which is useful for asymmetric ene reactions. Thus ozonolysis and remoeval of the water of hydration produces the glyoxylate in 89% yield (eq 10). 

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). Similarly, tin(I V) chloride-catalyzed ene reactions of 8-phenylmenthyl glyoxylates afford unsaturated secondary alcohols with 93-98% de of the (S) configuration. ... 

Addition of (/ )-menthyl glyoxylate (la) to 1-trimethylsilyloxy-l,3-butadiene (2e) proceeds with a selectivity comparable to that of 1-alkoxybutadicnes. Even (f )-8-phenylmenthyl glyoxylate (1 b), bearing a very efficient chiral auxiliary, adds to 1-trimethylsilyloxy-l,3-butadiene (2e) with low diastereoselectivity17. 

The reaction of (K)- or (Z)-vinylsilanes with 8-phenylmenthyl glyoxylate provides a single (2S)-alcohol (equation I). 

Chiral glyoxylic acid derivatives, i.e. (— )-8-phenylmenthyl glyoxylate, imdergoes an MBH reaction with cyclic a,p-unsaturated ketones under the... 

Asymmetric MBH were reported with (-)-menthyl and (-)-8-phenylmenthyl glyoxylates [155]. Only one of the possible diastereoisomers was observed in H NMR (Scheme 7.28). 

---