Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, UK OX1 3TA.
Org Biomol Chem. 2010 Sep 7;8(17):3975-84. doi: 10.1039/c004496b. Epub 2010 Jul 2.
Reaction of diazodiketoesters 17 and 28 with methyl glyoxylate in the presence of catalytic rhodium(II) acetate generates predominantly the 6,8-dioxabicyclo[3.2.1]octanes 29 and 30, respectively. Acid-catalysed rearrangement of the corresponding alcohol 31 favours, at equilibrium, the 2,8-dioxabicyclo[3.2.1]octane skeleton 33 of the squalestatins-zaragozic acids. Force field calculations on the position of the equilibrium gave misleading results. DFT calculations were correct in suggesting that the energy difference between 31 and 33 should be small, but did not always suggest the right major product. Calculation of the NMR spectra of the similar structures could be used to assign the isomers with a high level of confidence.
二氮杂二酮酯 17 和 28 在催化醋酸铑(II)存在下与甲基乙二醛反应，分别主要生成 6,8-二氧杂双环[3.2.1]辛烷 29 和 30。相应的醇 31 在酸催化下重排，在平衡时有利于鲨烯他汀-扎拉戈酸的 2,8-二氧杂双环[3.2.1]辛烷骨架 33。对平衡位置的力场计算给出了误导性的结果。DFT 计算正确地表明 31 和 33 之间的能量差异应该很小，但并不总是表明主要产物是正确的。类似结构的 NMR 光谱计算可用于高度置信度地分配异构体。
