The CD-Spiroacetal Subunit

The CD-spiroacetal subunit of the spongistatins proved to be of an appropriate level of complexity that several different synthetic strategies were evaluated. Access to the desired spiroacetal 5 was readily achieved by acid catalysed equilibration of the mixture of spiroacetals in aprotic solvents, followed by separation and recycling of the undesired isomer. Furthermore, the 1,5-anti aldol reaction of methyl ketones proved invaluable for construction of certain portions of the target molecule. 

Paterson, 1. and Coster, M.J. (2002) Total synthesis of altohyrtin A (spongistatin 1) an alternative synthesis of the CD- spiroacetal subunit C16-C28. Tetrahedron Lett., 43,3285-3289. 

Paterson, I., Wallace, D.J., and Gibson, K.R. (1997) Studies in marine macrolide synthesis synthesis of a C16-C28 subunit of spongistatin 1 (altohyrtin A) incorporating the CD-spiroacetal moiety. Tetrahedron Lett., 38, 8911-8914. 

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