C([N:3]([CH2:6]C)[CH2:4][CH3:5])C.C1(P(N=[N+]=[N-])(C2C=CC=CC=2)=[O:15])C=CC=CC=1.[S:25]1[C:34]2[C:29](=[CH:30][CH:31]=CC=2C(O)=O)[CH2:28][CH2:27][CH2:26]1.[C:38]([OH:42])([CH3:41])([CH3:40])[CH3:39]>C1(C)C=CC=CC=1>[C:38]([O:42][C:6]([NH:3][C:4]1[CH:5]=[CH:31][CH:30]=[C:29]2[C:34]=1[S:25][CH2:26][CH2:27][CH2:28]2)=[O:15])([CH3:41])([CH3:40])[CH3:39]At room temperature, 9.0 ml (64.4 mmol) of triethylamine, then 13.9 ml (64.4 mmol) of diphenylphosphoryl azide are added to 10 g (51.5 mmol) of thiochroman-8-carboxylic acid in 260 ml of toluene. The whole is heated at 90° C. for 2 hours, then 4.8 g (64.4 mmol) of tert-butanol dissolved in 10 ml of toluene are added dropwise and the temperature is subsequently maintained at 90° C. for a further 20 hours. The whole is allowed to cool and washed with 120 ml of water, 120 ml of 0.N hydrochloric acid, 120 ml of water, 120 ml of a saturated aqueous sodium hydrogen carbonate solution and 120 ml of water. After drying over magnesium sulphate and evaporation, the residue is taken up in cyclohexane and triturated, and a solid is removed by filtration; the filtrate is concentrated (13.3 g ) and then chromatographed on 1 kg of silica (eluant: dichloromethane) to yield 11.2 g of the desired product (yield: 82%).
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