A NOVEL-APPROACH TOWARD THE SYNTHESIS OF CHIRAL 2,3-DIDEOXY NUCLEOSIDES AND THEIR CARBOCYCLIC ANALOGS

Photochemical ring-expansion of chiral 2(S),3(R)-bis[(benzoyloxy) meth yl] cyclobutanone (3) in the presence of alcohols and acidic N-H funct ional groups gives anomeric mixtures of acetals and N-amino acetals, r espectively, with retention of stereochemistry of the ring substituent s. In the presence of purine and 6-chloropurine the corresponding prot ected nucleosides are-obtained. The photoadduct with 6-chloropurine is converted to the known medicinally active deprotected adenine nucleos ide with methanolic ammonia. One-carbon homologation of ketone 3 with diazomethane produces the corresponding optically pure cyclopentanone 8 with retention of stereochemistry. This ketone is converted to the o ptically pure cyclopentylamine 10 in two steps. Racemic amine 10 has b een used as a key intermediate in the preparation of carbocyclic nucle osides.