Compounds of formula I are provided where X
1
, X
2
and X3 are independently selected from H or hydroxy protecting groups. Such compounds are used in preparing pharmaceutical compositions and are useful in treating a variety of biological conditions.
提供式I的化合物,其中X1、X2和X3独立地选择自H或羟基保护基团。这些化合物用于制备药物组合物,并且在治疗各种
生物学疾病方面非常有用。