Camphor as a natural source of chirality in asymmetric synthesis

摘要: The readily available enantiomers of bornane[ 10,2]sultam serve as efficient, versatile and practical chiral auxiliaries. A selection highly r-face-selective reactions their N-enoyl derivatives (Diels-Alder additions, dihydroxylations, 1,4-additions) well 0-metalated N,O-ketene acetals (aldolizations, alkylations, brominations, "aminations") are described. Applications to the syntheses natural products and, particularly, enantiomerically pure a-amino acids demonstrate preparative potential. abundance, crystallinity manifold transformations camphor (+)-L (Scheme 1) have attracted considerable interest throughout history organic chemistry. By means various rearrangements functionalizations at C(3), C(5), C(8), C(9) C(lO), cleavage C(l)/C(2) C(2)/C(3) bonds, has served a fascinatingly starting material for products. This chemistry, which entails incorporation topicity into target molecules, been reviewed (ref. 1). Scheme 7 I Nu' (+I 1 (4 (+) -Camphor (-) Camphor Here we address issue non-destructive chirality transfer from (t)and (-)-camphor covalently bound auxiliary groups. Particularly, venerable C(lO)-sulfonation camphor, combined with conformational rigidity bornane skeleton spawned most successful development this field. Thus, bornane10,2-sultam (-)-J its antipode (t)-2, accessible inexpensive (-)camphorsulfonic in two simple operations were introduced 1984 rank today among auxiliaries 2) 3). Both chirophore commercially kg-quantities 3c).