Acetic acid, 2-(triphenylphosphoranylidene)-, methyl ester → Pentadecadienoic acid

To the trans-2-tridecenal (1.7 g) dissolved in methylene chloride (80 ml) was added (carbomethoxymethylene)triphenyl phosphorane (4.0 g), and the mixture was stirred for 2 hours. The reaction mixture was subjected to chromatography on a silica gel column with eluent systems of n-hexane-ethyl acetate (from 100:1 to 20:1) to give the methyl ester of trans,trans-2,4-pentadecadienoic acid (2.1 g). Potassium hydroxide (2.0 g) was dissolved in a mixed solvent of ethanol-water (1:1), and the methyl ester of trans,trans-2,4-pentadecadienoic acid (2.1 g). After the mixture was stirred at 60° C. for 40 minutes, it was cooled, adjusted to a weak acidic range of pH with citric acid and extracted with ethyl acetate. The ethyl acetate layer was dried over anhydrous sodium sulfate and concentrated to give trans,trans-2,4-pentadecadienoic acid (1.9 g). The product was dissolved in N,N-dimethylformamide (DMF, 50 ml), and para-nitrophenol (1.2 g) and N,N'-dicyclohexylcarbodiimide (1.7 g) were added. The mixture was stirred for 12 hours. After the reaction, precipitates produced were removed by filtration, DMF was removed by distillation, and the residue was subjected to chromatography on a silica gel column with eluent systems of n-hexane-ethyl acetate (from 200:1 to 50:1) to give the active ester of trans,trans-2,4-pentadecadienoic acid (1.3 g). To the active ester (600 mg) dissolved in DMF (30 ml) were added 6-(4'-N-glycyl-spicaminyl-amino)purine hydrochloride (750 mg) and triethylamine (1.2 ml). The mixture was stirred for 12 hours. After the solvent was removed by distillation, the residue was subjected to chromatography on a silica gel column with eluent systems of chloroform-methanol (from 7:1 to 5:1) to give SPK285 in the yield of 530 mg.