OPPOLZER Chiral reagent

OLOFSON Reagent 279 OPPENALIER Oxidation 280 OPPOLZER Chiral reagent 281 Ortoleva 218... 

The reagent has one handicap only (+)-pulegone is readily available. Consequently, Oppolzer and coworkers2 have examined a number of chiral alcohols, derived from various monoterpenes, in which the hydroxyl group is similarly shielded. The endo, e/.r-diphenylmethylisoboraeol (2), obtained from ( + )-camphor, and the enantiomer, obtained from ( —)-camphor, are almost as effective as 1 as chiral adjuncts in this Diels-Alder reaction. 

Oppolzer s chiral auxiliary,6 (-)-2,10-camphorsultam, is useful in the asymmetric Diels-Aider reaction,3.4 and for the preparation of enantiomerically pure p-substituted carboxylic acids7 and diols,8 in the stereoselective synthesis of A2-isoxazolines,9 and in the preparation of N-fluoro (-)-2,10-camphorsultam, an enantioselective fluorinating reagent.10... 

Oppolzer and coworkers [147, 454] have developed a class of reagents based on the enantiomeric bomane-2,10-sultam skeleton 1.133. These chiral auxiliaries are easily prepared from the enantiomeric 10-camphosulfonic adds [455]. Saturated or a,P-unsaturated TV-acylsultams 1.134, occasionally prepared from Af-silyl precursors [396], have been used very frequently. Asymmetric alkylations, animations and aldol reactions of enolates or enoxysilane derivatives of 1.134 (R = R CH2) [147, 404, 407, 456-460] are highly selective. The a,(3-unsaturated TV-acylsultams 1.134 (R = R R"C=CH) suffer highly stereoselective organocuprate 1,4-additions [147, 173], cyclopropanations [461], [4+2] and [3+2] cydoadditions [73,276,454,462], OSO4 promoted dihydroxylations [454,463] and radical addi-... 

Two other alkylations were based on readily-available chiral auxiharies. PhUippe Karoyan of the Universite Pierre et Marie Curie observed Tetrahedron Lett. 2008, 49, 4704) that the acylated Oppolzer camphor sultam 20 condensed with the Mannich reagent 21 to give 22 as a single diastereomer. Andrew G. Myers of Harvard University developed the pseudoephedrine chiral auxiliary of 23 to direct the construction of ternary alkylated centers. He has now established J. Am. Chem. Soc. 2008,130, 13231) that further alkylation gave 24, having a quaternary alkylated center, in high diastereomeric excess. 

Phenylsulfonyl)-3-phenyloxaziridine (1S6. Davis reagent. Figure 11.61) has been shown to react with sodium enolates of chiral carboximides of the Evans-Oppolzer type, providing a-hydroxyacyl derivatives with diastereoselectivities of 90-98% d. g 92,133 Subsequent titanium(IV) isopropoxide-mediated transesterification with benzyl alcohol and hydrogenolytic debenzylation releases the free a-hydroxy acids in enantiomerically pure form and in yields of 65-75%. This procedure was applied... 

Oppolzer s acylated camphorsultams (147, Equation 12) remain a classic among chiral auxiliaries for asymmetric synthesis and have been successfully applied in a variety of mechanistically distinct chemical transformations [88, 91]. The corresponding enolates can readily be prepared with a variety of strong bases and have been shown to undergo diastereoselective alkylation with a range of activated and non-activated electrophilic reagents. An illustrative example is the formation of 149 in dr >99 1 [91]. The sense... 

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