| 摘要 |
<p>The present invention relates to an improved process for the preparation of pentopyranosyl nucleosides, in which a significant improvement and simplification of the process step described in DE-A-19741715 can be achieved. Using the process according to invention, a migration of the 2'-acyl protective group from the 2'-position to the 3'-position of the pentopyranoside is brought about, a catalyst of the formula IVa or IVb being used In this formula, A is -CH2- or -NR<20>-, R<20 >is hydrogen, alkyl, cycloalkyl, aryl, aralkyl, each of which is optionally substituted, D is a group of the formula -CmH2m-, and m is an integer from 1 to 6, R<18>, R<19 >and R<24 >independently of one another, identically or differently, are hydrogen, alkyl, cycloalkyl, aryl or aralkyl, each of which is optionally substituted, or R<18 >and R<19 >are together a group -CoH20-, where o is an integer from 2 to 4, and R<21 >is a group -NR<22>R<23>, in which R<22 >and R<23 >independently of one another, identically or differently, are hydrogen, alkyl, cycloalkyl, aryl or aralkyl, each of which is optionally substituted.</p> |
