Optically Active Cyclobutanone Chemistry: Synthesis of (−)-Cyclobut-A and (±)-3‘-Epi-Cyclobut-A

The carbocyclic nucleoside analogues (−)-cyclobut-A and (±)-3‘- epi -cyclobut-A were synthesized utilizing photolysis of the (benzyloxymethyl)(methoxy) chromium carbene complex 4 with optically active ene-carbamate 5 to produce the corresponding optically active α,α-disubstituted cyclobutanone 6 . Stereoselective removal of the α-ethoxy group with inversion gave cyclobutanone 7, which was converted by existing methodology to the title compounds.