Asymmetric synthesis decane

Stereochemical control of intramolecular 1,3-dipolar cycloadditions by route b (Scheme 2.211) was realized in the asymmetric synthesis of l-azaspiro[4.5] decanes by using the chiral (2R)-bomane-10,2-sultam (X ) auxiliary in the dipo-larophilic fragment (Scheme 2.220) (718). 

In contrast to the abundant coverage of the intermolecular cycloaddition of 3-oxidopyridinium betaines [3, 87], relatively few intramolecular applications have been described. In this context, Peese and Gin have developed an efficient, asymmetric approach to the hetisine class of the C2o-diter-penoid alkaloids based on an intramolecular oxidopyridinium [5-1-2] cycloaddition in which simultaneous formation of the C5—C6 and CIO—C20 bonds in the 3-methyl-1-aza-tricyclo[5.2.1.0 ]decane core of these alkaloids was achieved [88]. As shown in Scheme 20.35, the heating of chiral oxidopyridinium betaine 81 in toluene at reflux produced the corresponding enantiopirre cycloadduct 82 in 77% yield. The latter constituted a potent intermediate for the asymmetric synthesis of the hetisine class of alkaloids, such... 

In 2001, Braga et al. reported the synthesis of new chiral C2-symmetric oxazolidine disulfide ligands from (R)-cysteine and successfully applied them as catalysts in the asymmetric addition of ZnEt2 to various aldehydes (Scheme 3.23). In the presence of 2mol% of ligand, excellent enantioselectivities of up to >99% ee were obtained even with aliphatic aldehydes such as n-decanal or n-hexanal. These authors proposed that the active catalyst did not maintain its C2-symmetry during the reaction. The disulfide bond was probably cleaved in situ by ZnEt2. 

Banks, M. R., Cadogan, J. I. G., Gosney, I., Grant, K. J., Hodgson, P. K. G., Thorburn, P. Synthesis of enantiomerically pure (5S)-4-aza-2-oxa-6,6-dimethyl-7,10-methylene-5-spiro[4.5]decan-3-one, a novel chiral oxazolidin-2-one from (-)-camphene for use as a recyclable chiral auxiliary in asymmetric transformations. Heterocycles 1994, 37,199-206. 

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