(1R, 5S)-(-)-6,6-DIMETHYL-3-OXABICYCLO3.1.0HEXAN-2-ONE. HIGHLY ENANTIOSELECTIVE INTRAMOLECULAR CYCLOPROPANATION CATALYZED BY DIRHODIUM(II) TETRAKISMET HYL 2-PYRROLIDONE-5(R)-CARBOXYLATE : ((3-OXABICYCLO3.1.0HEXAN-2-ONE, 6,6-DI METHYL-, (1R-CIS)-)