Bu3SnH-mediated radicalcyclization of α-bromo amide 8, bearing phenyl and phenylthio substituents at the terminus of the N-vinylic bond, proceeded in a 4-exo-trig manner to give β-lactam 9. Ruthenium tetroxide oxidation of the phenyl group incorporated into the product 9 provided a new synthesis of 4-oxo-2-azetidineaceticacid 13, a usuful intermediate for (±)-PS-5. Chiral 4-oxo-2-azetidineaceticacids 23 and
Bu 3 SnH介导的α-溴酰胺8的自由基环化,在N-乙烯基键的末端带有苯基和苯硫基取代基,以4 -exo-trig方式进行,得到β-内酰胺9。掺入产物9中的苯基的四氧化钌氧化提供了4-氧代-2-氮杂环丁烷乙酸13的新合成,4-氧代-2-氮杂环丁烷乙酸是(±)-PS-5的有用中间体。还通过N的不对称自由基环化获得了分别用于合成(+)-PS-5和(+)-硫霉素的关键中间体手性4-氧代-2-氮杂环丁烷乙酸23和36。-在侧链具有手性助剂的乙烯基-α-溴酰胺。
KITA, YASUYUKI;TAMURA, OSAMU;SHIBATA, NORIO;MIKI, TAKASHI, J. CHEM. SOC. PERKIN TRANS. PT 1,(1989) N0, C. 1862-1864
A stereoselective synthesis of the chiral thienamycin intermediate (16) involving a diastereoselective Michael addition and a silicon-induced Pummerer-type reaction is described. In a similar way, the key intermediate for(+)-PS-5 was also prepared from 4-(phenylsulfinylmethyl)butanamide (21).