1-phenyl-1,2,9,10-tetrahydro[1,4]oxazino[2,3,4-jk]carbazol-7(8H)-one → (R)-(-)-1-phenyl-1,2,9,10-tetrahydro[1,4]oxazino[2,3,4-jk]carbazol-7(8H)-one

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Reaction Steps

1-Phenyl-1,2,9,10-tetrahydro[1,4]oxazino[2,3,4-jk]carbazol-7(8H)-one (0.600 g) is dissolved in a minimum volume of chloroform and isopropanol is added to give a final volume of 15 mL. The solution is injected onto a 5×50 cm column of 20 micron Chiralcel OD (Chiral Technologies) held at 30° C. The sample is eluted with 30% isopropanol in heptane (V/V) at 75 mL/min while monitoring at 245 nm using a Merck/Sepracor ST-140 HPLC with closed loop peak shaving and recycling capability. About 70% of the front part of the broad peak that eluted between 25-32 minutes is collected and about 40% of the tail of the second peak that eluted between 29-37 minutes is collected. The central portions of these overlapping peaks are recycled and complete resolution is obtained on the second pass. The appropriate fractions are pooled and the solvent is removed on a rotary evaporator. The residues are assayed on a 0.46×25 cm Chiralcel OD-H column at ambient temperature using 25% isopropanol in heptane at 0.5 mL/min and detection at 244 nm. The earlier eluting enantiomer (0.297 g, Rt=21.7 min) assayed for 97.6% ee. Chromatography on silica gel using acetone/hexane (20/80) gave 0.296 g of (R)-(−)-1-phenyl-1,2,9,10-tetrahydro[1,4]oxazino[2,3,4-jk]carbazol-7(8H)-one; [α]D=81° (CH2Cl2). The eluting enantiomer (0.261 g, Rt=26.8 min) assayed for >99% ee. Chromatography on silica gel using acetone/hexane (20/80) gave 0.254 g of (S)-(+)-1-phenyl-1,2,9,10-tetrahydro[1,4]oxazino[2,3,4-jk]carbazol-7(8H)-one. [α]D=+84° (CH2Cl2).

Provenance & Evidence