the chair conformation. Ring D is in envelop conformation. The acetoxy and acetyl substituents are twisted with respect to the average molecular plane of the steroid. The twist along the length of the steroid molecule is negligible [C19–C10···C13–C18 = 2.3°]. In the crystal structure, the water molecule lies on a twofold axis which links the molecules into infinite supramolecular chains through OW–H···O
3β-Acetoxy-17α-hydroxy-16α-methylallopregnan-20-one,
C24H38O4·0.5H2O,是合成
地塞米松(一种重要的
皮质类
固醇)的
中间体。该化合物在单斜空间群 C2 中结晶,晶胞参数为:a = 10.665(2) Å,b = 7.497(1) Å,c = 28.200(4) Å,β = 92.74(2)°,Z = 4。晶体结构已通过直接方法求解,并针对 1579 次观察到的反射精制至 R = 0.0419。类
固醇骨架的所有环都是反式连接的。环A、B和C都在椅子构象中。环 D 呈信封构象。乙酰
氧基和
乙酰基取代基相对于类
固醇的平均分子平面是扭曲的。沿类
固醇分子长度的扭曲可以忽略不计[C19–C10…C13–C18 = 2.3°]。在晶体结构中,