| 摘要 |
Intermediates (I) for prepg. cephalosporins are new. R1=lower alkyl or (un)substd. Ph, R2=alkoxycarbonyl, R5=lower alkyl or (un)substd. allyl. Stir a mixt. of ethyl 2-aminothi azole-4-ylacetate 186g (1mol), DMS 300mL and 98% di-tertiarybutylpyrrocarbonate 500g (2.3 mol) for 1 week at room temp., and ice water 3.5L, suck filter and wash cake with water 2L, pour in CH2Cl2 2L, dry CH2Cl2 phase with Na2SO4 after separating water, conc. by rotatory evaporator and immediately crystallize in petroleum ether 2L to give ethyl 2- tertiary-butoxycarbonylimino-3tertiary-butoxy-4-thiazolin-4-ylacetate (yield=78%, m.p=90 deg.C).
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