A synthesis of a common intermediate to the lactone–pyrrolidinone ring systems in oxazolomycin A and neooxazolomycin
作者:Nicholas J. Bennett、Jeremy C. Prodger、Gerald Pattenden
DOI:10.1016/j.tet.2007.03.043
日期:2007.7
the bromoamide 34 derived from the enantiopure α-ethynyl substituted amino alcohol 31 led to a 2:1 mixture of β-C3 and α-C3 methyl epimers of the pyrrolidinone 35a–36a in a combined yield of 73%. Treatment of the homoallylic alcohol 35b, derived from 35a, with OsO4–TMEDA, gave a single diastereoisomer of the pyrrolidinone triol 37, resulting from selective dihydroxylation from the β-face, i.e. syn to
对映体纯的α-乙炔基取代的氨基醇31衍生的溴酰胺34的5- exo- dig自由基环化导致吡咯烷酮35a – 36a的β-C3和α-C3甲基差向异构体混合物2:1混合产生占73%。用OsO 4 -TMEDA处理35a衍生的均丙醇35b,得到了吡咯烷酮三醇37的单一非对映异构体,这是由β面(即与35b的CH 2 OH基团合成)进行选择性二羟基化而产生的。吡咯烷酮三醇37是潜在的常见前体,请参见。如图9所示,在恶唑球霉素A(1)和新恶唑球霉素2中分别形成螺-β-内酯吡咯烷酮8和γ-内酯吡咯烷酮10环系统。在1,2-二醇官能顺序保护37作为丙酮化合物39,并在伯醇基团39为SEM醚41A,随后在氮中心的甲基41A,使用的NaH-将MeI,然后得到选择性保护吡咯烷酮42。