The syntheses of (-)- and (+)-homononactic acid were achieved in 4 steps and 6 steps, respectively, starting with the reaction of 2-lithio-5-vinylfuran and (S)-(-)-ethyloxirane. The vinyl group was transformed to the branched aldehyde by a regiospecific oxo reaction. Oxidation to the carboxylic acid, esterification, and hydrogenation of the furan ring formed four diastereomers of methyl homononactate. Two of these isomers were used directly for the synthesis of tetranactin, the others could be recycled by epimerisation and separation. The achiral macrolide antibiotic was constructed from two molecules of chiral (+)-homononactyl-(-)-homononactic acid by ester formation via the acid chloride and subsequent lactonisation via the (active) thiocarboxylic S-(3-cyano-4,6-dimethyl-2-pyridinyl) ester. The structure of isodinactin was corrected by comparing the optical rotations of methyl nonactate and methyl homononactate from natural origin with those of the optically pure synthetic compounds.
以2-
锂硫基-5-
乙烯基呋喃和(S)-(-)-乙基
环氧乙烷的反应为起始点,分别经过4步和6步合成(-)-和(+)-高
月桂酸。通过区域特异性氧化反应将
乙烯基转化为支链醛。
呋喃环氧化成
羧酸、酯化和氢化形成四种均
壬酸甲酯的非对映体。其中两种异构体直接用于四联菌素的合成,其他异构体可以通过差向异构化和分离进行回收。非手性大环
内酯类抗生素由两分子手性 (+)-高单酰基-(-)-高单酰基通过酰基
氯形成酯并随后通过(活性)
硫代
羧酸 S-(3-
氰基-4,6-) 内酯化而构建。二甲基-2-
吡啶基)酯。通过比较天然来源的九
乙酸甲酯和高九
乙酸甲酯与光学纯合成化合物的旋光度,校正了
异丁酸的结构。