C[O:2][C:3](=O)[C@H:4]([CH2:16][CH:17]([CH3:19])[CH3:18])[NH:5][C:6]([O:8][CH2:9][C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=1)=[O:7].[H-].C([Al+]CC(C)C)C(C)C.CO.C(C(C(C([O-])=O)O)O)(O)=O.[K+]>C1(C)C=CC=CC=1>[CH2:9]([O:8][C:6]([NH:5][C@H:4]([CH:3]=[O:2])[CH2:16][CH:17]([CH3:18])[CH3:19])=[O:7])[C:10]1[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=1A solution of (S)--N--(benzyloxycarbonyl)leucine methyl ester (8.22 g, 29.4 mmol) in dry toluene (80 ml) was treated dropwise at -78° C. with a solution of di-iso-butylaluminium hydride (1.0 M, 74 ml, 74 mmol) in toluene. The solution was stirred at -78° C. for 30 min. before methanol (3.5 ml) was added to quench the reaction. The cold mixture was then added to a stirred aqueous solution of potassium hydrogen tartrate (200 ml). After further stirring for 1 hour the mixture was extracted with ether (3×200 ml), the combined extracts washed with brine (400 ml), dried (MgSO4) and evaporated in vacuo to provide the title compound as a colourless oil. This material was used without purification in the next step.
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