Total Synthesis of Angucyclines. XVII. First Synthesis of Antibiotic 100‐1, a Deoxydisaccharide Angucycline Antibiotic of the Urdamycinone B‐Type
作者:Karsten Krohn、Attila Agocs、Christiane Bäuerlein
DOI:10.1081/car-120026460
日期:2003.12.31
Two routes to the deoxydisaccharide angucycline antibiotic 100‐1 (3) are described. Key steps comprise the regioselective oxidation/bromination of the 1,5‐diacetoxyolivose C‐saccharide 7 to the bromoquinone 8. Diels–Alder reaction of the bromoquinone with the diene 9 followed by HBr elimination afforded the urdamycinone B precursor 11 as a diastereomeric mixture. Selective protection as the TBDMS ether
描述了两种脱氧二糖古环素抗生素100-1(3)的途径。关键步骤包括1,5- diacetoxyolivose的区域选择性氧化/溴化Ç -saccharide 7到bromoquinone 8。溴醌与二烯9的Diels-Alder反应,然后去除HBr,从而得到了乌达霉素B前体11,为非对映异构体混合物。选择性保护的TBDMS醚13,乙酰化和得到醇的甲硅烷基醚脱保护15将其选择性地被糖基化,以α-rhamnal糖苷17使用苯甲酰rhamnal以72%的产率(在70%转化率)(16)作为糖苷供体,三氟甲磺酸scan作为促进剂。然后将糖苷配基的C-3处的甲硅烷基转化为羟基。然后将Zemplén在C-1处的苄基脱酰并进行光氧化,将这两种非对映异构体转化为天然产物3和C-3非对映异构体20。在这一阶段,非对映异构体3和20被分离。替代地并且更容易地,在urdamycinone B类似物21a和21b的