[C:1]([O:5][C:6]([N:8]1[CH2:13][CH2:12][CH2:11][CH2:10][CH:9]1[C:14]([OH:16])=O)=[O:7])([CH3:4])([CH3:3])[CH3:2].ClC(OCC(C)C)=O.[N+:25](=[CH2:27])=[N-:26].CC1C=CC(S(N(N=O)C)(=O)=O)=CC=1.[OH-].[K+].C(OCCOCCO)C>O1CCCC1.C(OCC)C.O.C(N(CC)CC)C>[C:1]([O:5][C:6]([N:8]1[CH2:13][CH2:12][CH2:11][CH2:10][CH:9]1[C:14](=[O:16])[CH:27]=[N+:25]=[N-:26])=[O:7])([CH3:2])([CH3:3])[CH3:4]
To a solution of piperidine-1,2-dicarboxylic acid 1-tert-butyl ester (3.0 g in a mixture of 26 mL dry tetrahydrofuran and 26 mL dry diethyl ether) at -10° C. was added 1.91 mL of triethylamine followed by the dropwise addition of 1.78 mL isobutyl chloroformate. The reaction was stirred at -10° C. for 30 minutes then warmed to 0° C. Over the next hour, 26 mL of a solution of diazomethane in diethyl ether was added (prepared from: 8.0 g Diazald® in 70 mL diethyl ether; 4g potassium hydroxide; 20 mL 2-(2-ethoxyethoxy)ethanol; 6 mL water and 12 mL diethyl ether using a mini Diazald Kit) and the mixture allowed to stir at room temperature for an additional 2 hours. At this time the reaction was quenched by the addition of 3 mL acetic acid at 0° C. This was then diluted with 100 mL water and 100 mL diethyl ether, the layers separated and the aqueous portion extracted with (2×75 mL) diethyl ether. The combined organics were washed with water (75 mL), saturated sodium bicarbonate (2×75 mL) and brine (75 mL) then dried over magnesium sulfate. Removal of the solvent in vacuo and purification of the residue by flash chromatography on silica gel (hexane:ethyl acetate, 8:2) gave the title compound (2.99 g).
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