SYNTHESES AND CD STUDIES OF 5-ALPHA-CHOLESTENO[3,2-D]PYRIMIDINES, 5-ALPHA-CHOLESTENO[2,3-D]PYRIMIDINES AND 5-ALPHA-CHOLESTENO[3,4-D]PYRIMIDINES

Syntheses of 5 alpha-cholesteno[3,2-d]- (5a), [2,3-d]- (12a), and [3,4 -d]pyrimidines (15a) have been achieved by using hydroxymethylene deri vatives of relevant cholestanones prepared from cholesterol (1). Their CD spectra exhibit at least three Cotton effects between 300 to 200 n m, a first CD band around 290, a second one around 260 and a third one around 220 nm. A quadrant rule is developed and applied to the determ ination of the sign of the first CD band, while a helicity rule is app licable to the third CD band. The first band is positive in the [3,2-d ] series, whereas it is negative in the [2,3-d] and the [3,4-d] series . The third band is negative in all three series.