| 摘要 |
A process for the preparation of a compound of formula (I) or a pharmaceutically acceptable salt thereof: <CHEM> wherein R1, R2 and R3 are as defined in formula (A); and in which any OH groups in R1, R2 and/or R3 may be in the form of O-acyl, phosphate, cyclic acetal or cyclic carbonate derivatives thereof; which process comprises the ring closure of a compound of formula (II): <CHEM> wherein Ra is amino or a group or atom convertible thereto; Rb is amino or an amino derivative and R1 min , R2 min and R3 min are R1, R2 and R3 respectively or R1, R2, and/or R3 wherein OH group(s) is/are protected; and thereafter converting Ra when other than amino, to amino; R1 min to R1, R2 min to R2 and/or R3 min to R3 when necessary and/or optionally forming a pharmaceutically acceptable salt or derivative thereof as defined. |
