Intramolecular processes stereochemical effects

A series of innovative investigations by Kiyooka and co-workers have introduced the use of tandem reaction processes that commence with a stereoselective aldol addition reaction and are followed by C=0 reduction [13]. A chiral oxazaboroli-dine complex prepared from BH3-THF and A-/ -toluenesulfonyl (L)-valine controls the absolute stereochemical outcome of the aldol reaction. In a subsequent reaction, the /i-alkoxyboronate effects intramolecular reduction of the ester to furnish the corresponding /i-hydroxy aldehyde. 

Our exploration of the intramolecular palladium(II)-catalyzed alkoxy carbonylation reaction had yielded useful insights into the scope of this cyclization process, which turned out to be highly dependent on subtle conformational effects. Ironically, the only stereochemical configuration of an appropriately substituted oxane that we could not directly access using this methodology was that required for a synthesis of... 

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