[F:1][C:2]1[CH:7]=[CH:6][C:5]([C:8]2[CH2:13][CH:12]([N:14]3[CH2:18][CH2:17][CH2:16][CH2:15]3)[CH2:11][C:10]([CH3:20])([CH3:19])[C:9]=2[CH:21]=O)=[CH:4][C:3]=1[CH3:23].[Li+].CC([N-]C(C)C)C.C(=NC1CCCCC1)C.[C:41]([OH:46])(=O)[C:42](O)=O>CCOCC.O.C([O-])(O)=O.[Na+]>[F:1][C:2]1[CH:7]=[CH:6][C:5]([C:8]2[CH2:13][CH:12]([N:14]3[CH2:15][CH2:16][CH2:17][CH2:18]3)[CH2:11][C:10]([CH3:19])([CH3:20])[C:9]=2/[CH:21]=[CH:42]/[CH:41]=[O:46])=[CH:4][C:3]=1[CH3:23]In a manner similar to Scheme I, 32 (3.80 g, 12.1 mmol) was treated with the LDA-derived anion of ethylidenecyclohexylamine (2.90 g, 23.2 mmol) in anhydrous ether. Workup and purification of the residue by HPLC using 1% Et3N in 10:1 hexanes:EtOAc as eluent provided the dieneimine (2.4 g). The imine and oxalic acid (10 g) in 40 mL H2O was heated at 100° C. for 2 h, cooled, diluted with saturated NaHCO3 and ether. The organic layer was washed with H2O and brine and dried (MgSO4). Removal of volatiles in vacuo provided 2.27 g of gum which was taken forward without further purification.
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