[CH2:1]([O:3][C:4](=[O:20])[CH2:5][N:6]=C(C1C=CC=CC=1)C1C=CC=CC=1)[CH3:2].C[Si]([NH-])(C)C.C[Si]([NH-])(C)C.[Na+].[Na+].Br[CH2:34][CH2:35][CH2:36][CH:37]1[NH:41][C:40](=[O:42])[CH2:39][CH:38]1[CH3:43]>C1COCC1>[NH2:6][CH:5]([CH2:34][CH2:35][CH2:36][CH:37]1[CH:38]([CH3:43])[CH2:39][C:40](=[O:42])[NH:41]1)[C:4]([O:3][CH2:1][CH3:2])=[O:20]A solution of N-(diphenylmethylene)glycine ethyl ester (Aldrich, 37 mmol) in THF (20 mL) is added to -72° C. solution of sodium bis (trimethylsilylamide) (35 mmol, 0.5 M in THF), while the solution is kept below -65° C. The resulting solution is then stirred at -72° C. for 30 min.; followed by the rapid addition of a cooled solution (-72° C.) of the product from EXAMPLE 236 (24 mmol) in THF via canula. The cooling bath is removed immediately and the mixture allowed to warm to 0° C. for 4 h. The reaction mixture is partitioned between ether and 10% aqueous sodium bisulfate, then-dried and concentrated. The product is purified by column chromatography. This intermediate is then treated with 0.1 N aqueous hydrochloric acid for 3 h, followed by extraction with ether and lyophilization of the aqueous solution, to yield the title material.
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