| 摘要 |
Compounds of the formula I in which X denotes fluorine or chlorine are prepared by reacting fluorosulphonyl isocyanate or chlorosulphonyl isocyanate with diketene, acetoacetyl fluoride, acetoacetyl chloride, acetic acid or with an isopropylene ester at temperatures from -35 to +70 DEG C. The isopropylene ester has the formula CH2=C(OOCR)-CH3, where R denotes an alkyl radical having 1 to 4 C atoms or an optionally substituted phenyl or benzyl radical. The resulting compounds of the formula I in which X represents F can, if desired, be converted into a compound of the formula VI, which is a known sweetener, by ring opening using water and cyclisation by means of bases. <IMAGE> |
