主权项 |
1. A compound of formula I, or pharmaceutically acceptable salt thereof: wherein,
each of R1, R2, R3, and R4 is independently H, —C(O)alkyl or —C(O)(CH2), CH3;wherein at least one R1, R2, R3, and R4 is H and at least one R1, R2, R3, and R4 is —C(O)alkyl or —C(O)(CH2)nCH3;each n is independently an integer from 0-18; and R is alkyl or alkenyl, each of which is optionally substituted with 1-4 substituents selected from acyl, oxo, azido, aryl, halogen, —OC(O)alkyl, or —SC(O)alkyl. |