SYNTHESES AND CD STUDIES OF NEW CHOLESTENO[4,3-D]PYRIMIDINES AND CHOLESTENO[7,6-D]PYRIMIDINES

The syntheses of 5 alpha- and 5 beta-cholest-3-eno[4,3-d]pyrimidines ( 7) and (7') could be achieved by using the hydroxymethylene derivative of cholestan-4-one (5) prepared from cholesterol (1). Their 2'-deriva tives 7a-7d and 7'a-7'c were also synthesized. 5 alpha-Cholest-6-eno[7 ,6-d]pyrimidine (13) was prepared by the reaction of 5 alpha-cholestan -7-one (12) with tris(formylamino)methane. The CD spectra exhibit at l east three Cotton effects between 300 and 210 nm, a first CD band arou nd 290, a second one around 260, and a third one around 220 nm. An ear lier developed quadrant rule can be applied to the determination of th e sign of the first CD band, while the suggested helicity rule allows prediction of the third CD band.