[H-].[Na+].[C:3]([C:5]1[CH:6]=[CH:7][C:8]2[O:13][C:12]([CH3:15])([CH3:14])[C@@H:11](Br)[C@H:10](O)[C:9]=2[CH:18]=1)#[N:4].C[Si](C)(C)[O:21][CH:22]1[CH2:26][CH2:25][NH:24][C:23]1=[O:27].[OH2:30]>CS(C)=O>[C:3]([C:5]1[CH:6]=[CH:7][C:8]2[O:13][C:12]([CH3:15])([CH3:14])[C@@H:11]([OH:30])[C@H:10]([N:24]3[CH2:25][CH2:26][CH:22]([OH:21])[C:23]3=[O:27])[C:9]=2[CH:18]=1)#[N:4]Sodium hydride (80% dispersion in oil, 1.6 g) was added to a solution of (±)-6-cyano-3,4-dihydro-2,2-dimethyl-trans-3-bromo-4-hydroxy-2H-1-benzopyran (14.86 g) in DMSO (100 mL) and the mixture stirred under a dry atmosphere for 45 min when a solution of the 3,4-epoxide resulted. The solution was then cooled to ca 10° C. before 3-trimethylsilyloxy-2-pyrrolidinone (12.86 g) was added along with further DMSO (20 mL) and sodium hydride (2.35 g). The mixture was stirred at room temperature for 22 h after which it was poured into water (600 mL) and extracted with ethyl acetate several times. The combined extracts were washed with water (4×150 mL), brine and dried (Na2SO4). Evaporation gave a crystalline greenish solid (14.4 g) which was triturated with a little ethyl acetate before filtering under suction and washing with a little ethyl acetate followed by 50% ether/ethyl acetate. The crystalline material (7.9 g, 50%) appeared to be a ca 50:50 mixture of the 3'-hydroxy isomers.
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