SYNTHESIS OF CYCLOCHOLATES AND DERIVATIVES - PART II - SELECTIVE SYNTHESIS OF CYCLOTETRACHOLATES FROM LINEAR DIMERS

Selective synthesis of cyclic tetramers 3 and hexamers 4 of cholic aci d was achieved from the cycloesterification of dimeric cholic acids 2 by using 2,6-dichlorobenzoyl chloride and 4-dimethylaminopyridine (DMA P). The results suggest that the cyclotetramer is the preferred even o ligomeric cycle size for both cholic acid and the 24-norcholic acid sy stem, consistent with our previous results for lithocholic acid. The s tructures of all dimeric hydroxy acids and cyclooligomers were determi ned by H-1 NMR, C-13 NMR and mass spectrometries.