The title synthesis was achieved by featuring diastereoface-selective cyclopropanation of (4R,5S)-4Jdiphenyl-3-vinyl-2-oxazolidinone and its related compounds, the chiral conformationally rigid N-vinylcarbamates, with sine-monojluorocarbenoid, followed by hydrogenolysis of the major addition products. The diastereofaceselectivity of the cyclopropanation could be explained by the most stable conformation of 3-vinyl
-2-oxasolidinone derivatives and attack from the less hinderedface of the conformer. DU-6859 (1) was found as the new generation of quinolonecarboxylic acid exhibiting marked antibacterial activity and little side effects. 4 It has been disclosed that the pronounced characteristics of 1 are closely related with its (lR,2S)-2-fluorocyclopropylamine [(lR,2S)-2)] moiety.5 In the preceding paper,6 it was reported that dl-2 can be readily prepared from benzylamine derivatives by employing c&selective cyclopropanation of N-benzyl-N-vinylcarbamates with zinc-monofluorocarbenoid. However, no asymmetric induction was achieved when N-[(R)-I-phenylethyll-N-vinylcarbamates (A) derived from (R)-1-phenylethylamine were employed as the reaction substrates. Accordingly, the preparation of (lR, 2S)-2 was accomplished by optical resolution of dl-2 with I-menthyl chlorofonnate or less effectively by separation of diastereomeric (lR,2S)-and (lS,2R)-N-[(R)-l-phenylethyl]-2-fluorocyclopropylamine ptoluenesulfonate derived from A. Since it has been uncovered by means of NOE experiments that the vinyl DU-6859 (1) (lR,2S)-2 A B ' 67 (84) 65:25:6:4 OMe a) Otherwise noted, all the reactions were carried out in dichloromelhane (CHzCl2) by employing fluorodiiodomethaoe (3.0 eq), diethylzinc (1.0 M solution in hexane, 3.0 eq.), ethers (3.0 eq.), and MS4A (equal weight to 6a). b) The yields in parenthesis were corrected for the recovery of 6a. c) Determined by the 19F-NMR spectrum. d) Diethyl ether (Et20) was used as a solvent. e) 1,2-Dimethoxyethane. f) A 1.0 M solution of dielhylzinc in CH2CI2 was used. g) 1,2-Diethoxyelhane.