| Popis: |
The syntheses of 5α- and 5β-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′-derivatives 7a-7d and 7′a-7′c were also synthesized. 5α-Cholest-6-eno[7,6-d]pyrimidine (13) was prepared by the reaction of 5α-cholestan-7-one (12) with tris-(formylamino)methane. The CD spectra exhibit at least three Cotton effects between 300 and 210 nm, a first CD band around 290, a second one around 260, and a third one around 220 nm. An earlier developed quadrant rule can be applied to the determination of the sign of the first CD band, while the suggested helicity rule allows prediction of the third CD band. |
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