Disclosed are processes for preparing compounds of the formula (I) and pharmaceutically acceptable salts or esters thereof: ##STR1## wherein R.sub.2 is a purine or pyrimidine base or an analogue or derivative thereof; and Z is S, S.dbd.O or SO.sub.2. The invention also relates to intermediates of use in the preparation of these compounds.
揭示了制备式(I)化合物及其药用可接受盐或酯的过程:##STR1## 其中R.sub.2是
嘌呤或
嘧啶碱基或其类似物或衍
生物;Z为S、S.dbd.O或SO.sub.2。该发明还涉及在制备这些化合物过程中使用的中间体。