Petard oxidation of methyl 2-thialaurate [CH3(CHT.)9--S--COOCH3, 1] gave methyl (decylsulfinyl)formate [CH3(CH2)9--SO---COOCH 3, 2]. Compound 2 reacted spontaneously with silica gel to give decyl decanethiolsolfinate [CH3(CH2)9--SO--S--(CH2)gCH 3, 3] in 84% yield. Thin layer chromatography of carbomethoxy 4-carbomethoxybutyl sulfoxide [CH3OOC(CH2)4---SO---COOCH3, ffJ on silica gel furnished 4-carbomethoxybutyl 4-carbomethoxybutanethiolsulfmate [CH3OOC(CH2)4--SO--S--(CH2)4~H3, 6, 63%]. When a mixture of compounds 2 and 5 was Β’hrom.atographed on silica gel, a mixture of decyl 4-carbomethoxybutanethiolsulfinate [CH3(CH2)9--S--SO---(CH2)4COOCH3, 7] and 4-carbomethoxybutyl decanethiolsulfmate [CH3(CH2)9--SO--S--(CH2)4COOCH 3, 8] was obtained in 20.2% yield in addition to compounds 3 (38%) and 6 (32%). Compound 7 was confh-n~l by coupling the sulfmyl chloride derivative of methyl 5-mercaptopentanoate with decanethiol. Compound 8 was prepat~ from the sulfinyl chloride derivative of decanethiol and methyl 5-mercaptopentanoate. The thiolsulfmate group gave a c~'stic absorption peak at about 1080 cm -] (S~-O, str.) in the infrared spectrum. The chemi~l shifts of the protons of the methylene groups adjacent to the thiolsulfmate group appeared at 8 3.12 (t, J = 7.5 Hz). In the 13C-NMR analysis, the shifts of the methylene carbon atoms adjacent to the thiolsulfinate group appeared at -32 (--SO--S--CH2--) and at 55 (--S--SO---CH2--) ppm.