通过使E -1,2-环氧-2-甲基-6,6-二甲氧基己-3--3-烯(5)与配位不饱和羰基铁反应生成的π-烯丙基三羰基铁内酯配合物(7)与苄胺通过类S N '机理生成内酰胺配合物(8)。用Ce(IV)氧化该络合物得到顺式-3-异丙烯基-4-[(2',2'-角(9)),将其化学修饰成反式-3-(1'-羟乙基)-4-[( 2',2-二甲氧基)乙基]氮杂环丁烷-2-酮(13),先前曾用于合成抗生素硫霉素的关键中间体,与(S)-(-)-α-甲基苄基胺提供了非对映异构体内酰胺铁配合物的可分离混合物(16和17)。这些复合物可以单独转化为相应的旋光性β-内酰胺衍生物(27和28),因此,它们是合成天然(+)-硫霉素或非天然(-)-硫霉素的前体。
An asymmetricsynthesis for the syntheticintermediates to carbapenem antibiotics was examined via isoxazoline derivatives prepared by 1,3-dipolar cycloaddition between the nitrile oxide and menthyl crotonate. The (4S)-trans-azetidinone (14) having the antipodal configuration of thienamycin was synthesised in 16–20% e.e., while 85.3% e.e. of the (4R)-cis-azetidinone, possessing the same absolute configuration