[CH2:1]([CH:4]([CH2:8][CH2:9][CH3:10])[C:5]([OH:7])=O)[CH2:2][CH3:3].C(Cl)(=O)[C:12]([Cl:14])=O.[N+](=C)=[N-].Cl.O1CCOCC1>ClCCl.CN(C=O)C>[Cl:14][CH2:12][C:5](=[O:7])[CH:4]([CH2:1][CH2:2][CH3:3])[CH2:8][CH2:9][CH3:10]To 2-propylpentanoic acid (156.6 μl, 1.00 mmol) dissolved in anhydrous dichloromethane (2 mL) was added DMF (3 μL, 4 mole %), and the solution was cooled to 0° C. under a nitrogen atmosphere. To the solution was added oxalyl chloride (94.3 μL, 1.08 mmol) dropwise over a few minutes. The reaction was stirred 18 hours while warming to ambient temperature. The mixture was cooled to 0° C. and excess ~0.3M ethereal diazomethane solution was added. The reaction mixture was stirred 18 hours while warming to ambient temperature. The reaction mixture was washed with 1M aqueous sodium carbonate solution (30 mL), dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue was dissolved in ether (2mL) and cooled to 0° C. under a nitrogen atmosphere. Hydrogen chloride as a 4N solution in dioxane (275 μL, 1.10 mmol) was added dropwise over a few minutes. The reaction was stirred 18 hours while warming to ambient temperature. The reaction mixture was concentrated under reduced pressure and the residual oil was used in the next step without further purification.
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