title: Synthesis of the C1-C28 Portion of Spongistatin 1 (Altohyrtin A).
abstract: A synthetic approach was developed to the C1-C28 subunit of spongistatin 1 (altohyrtin A, 65). The key step was the coupling of the AB and CD spiroketal moieties via an anti-aldol reaction of aldehyde 62 and ethyl ketone 57. The development of a method for the construction of the AB spiroketal fragment is described and included the desymmetrization of C(2)-symmetric diketone 10 and the differentiation of the two primary alcohols of 16. Further elaboration of this advanced intermediate to the desired aldehyde 62 included an Evans' syn-aldol reaction and Tebbe olefination. The synthesis of the CD spiroketal fragment 56 involved the ketalization of a triol-dione, generated in situ by deprotection of 45, to provide a favorable ratio (6-7:1) of spiroketal isomers 46 and 47, respectively. The overall protecting group strategy, involving many selective manipulations of silyl protecting groups, was successfully developed to provide the desired C1-C28 subunit of spongistatin 1 (altohyrtin A) (65).
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720.
authors.forename: Michelle M.
authors.initials: MM
authors.lastname: Claffey
authors.forename: Christopher J.
authors.initials: CJ
authors.lastname: Hayes
authors.forename: Clayton H.
authors.initials: CH
authors.lastname: Heathcock