Studies towards a stereocontrolled synthesis of the tricarboxylate core of the zaragozic acids–squalestatins by a cycloaddition–rearrangement strategy
作者:David M. Hodgson、Carol Villalonga-Barber
DOI:10.1016/s0040-4039(00)00873-x
日期:2000.7
Reaction of diazoketodiester 11 with methyl glyoxylate in toluene in the presence of catalytic rhodium(II) acetate gives predominantly the 6,8-dioxabicyclo[3.2.1]octane 13. Acid-catalysed rearrangement of the corresponding alcohol 14 favours at equilibrium the 2,8-dioxabicyclo[3.2.1]octane skeleton 15 of the zaragozic acids–squalestatins.
Synthetic and computational studies on the tricarboxylate core of 6,7-dideoxysqualestatin H5 involving a carbonyl ylide cycloaddition–rearrangement
作者:David M. Hodgson、Carolina Villalonga-Barber、Jonathan M. Goodman、Silvina C. Pellegrinet
DOI:10.1039/c004496b
日期:——
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 squalestatinsâzaragozic 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.