Ha. Kwon et al., STEREOCONTROLLED SYNTHESIS OF 4-ACETOXY-2-AZETIDINONE VIA DOUBLE AZETIDINONE RING FORMATION - A USEFUL PRECURSOR OF CARBAPENEM AND PENEM ANTIBIOTICS, Bulletin of the Korean Chemical Society, 18(5), 1997, pp. 475-478
R-tert-butyldimethylsilyloxy)ethyl]-2-azetidinone, one of the best syn
thons for carbapenems and penems was efficiently synthesized from read
ily available L-threonine via double azetidinone ring formation.