RIBOFURANOSE-RING CLEAVAGE OF PURINE NUCLEOSIDES WITH DIISOBUTYLALUMINUM HYDRIDE - CONVENIENT METHOD FOR THE PREPARATION OF PURINE ACYCLONUCLEOSIDES

The reaction of 2',3'-O-isopropylidene protected purine nucleosides wi th diisobutylaluminum hydride (DIBAL-H) caused the reductive cleavage of the C-1'-O-4' bond to give the corresponding 9-D-ribitylpurines. Th e ring cleavage of inosine 1a, thioinosine 1f, and their derivatives h aving an alkyl group at the O-6- or S-b-position 1c, e, and g proceede d smoothly to afford the corresponding ribityl derivatives 2a, f, c, e , and g, whereas N-6-methylated adenosine derivatives 1k and 1 remarka bly resisted the DIBAL-H reduction. 5'-Deoxy and 5'-chloro-5'-deoxy de rivatives 1b, d, i, and j also underwent reductive cleavage at the sug ar moiety under similar conditions. An acyclic analog of guanosine 6, which is of biological interest, was prepared from a guanosine derivat ive 5 in a similar way. The present methodology for the synthesis of p urine acyclonuculeosides was also applied to the preparation of an acy clic analog 17 of neplanocin A. (C) 1997 Elsevier Science Ltd.