The Nine Contiguous Chiral Centers in Streptovaricin A via Pyranosidic Homologation

Article abstract of DOI:10.1021/jo00284a030

A tripyranoside 2 has been prepared whose 10-carbon chain is folded so as to afford mutual internal protection of acetal groups.A cis-anti-trans-stereosurface is thereby provided which allows for stereocontrolled development of eight of the nine contiguous asymmetric centers of the ansa chain of streptovaricin A.The "upper" acetal ring is cleaved, and the ninth stereocenter is installed in intermediate 10 by using acyclic stereocontrol principles.The remaining acetal is then opened, and the functional groups exposed thereby are manipulated.All nine stereocenters are created with high stereoselectivity, and the termini of the resulting array, 14b, are suitably differentiated for eventual coupling with the pseudoaromatic residue.