Stereocontrol of 5,5-spiroketals in the synthesis of cephalosporolide H epimers.
A blueprint for controlling the stereochemistry of oxygenated 5,5-spiroketals using chelation effects is provided. Chelation specifically of zinc salts (other protic and Lewis acids were less effective) between the spiroketal oxygen and an appropriately positioned alcohol group overrides normal biases in the preparation of 5,5-spiroketals, as illustrated by the stereocontrolled synthesis of epimeric cephalosporolide H isomers. This study provides new and valuable information for prescribing the chirality of the stereogenic core of 5,5-spiroketals.
Tlais
Sami F
SF
Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, USA.
Dudley
Gregory B
GB
D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D001688:Biological Products / Q000737:chemistry; D005663:Furans / Q000737:chemistry*; D006900:Hydroxylation; D015394:Molecular Structure; D013141:Spiro Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D013237:Stereoisomerism
D001688:Biological Products; D005663:Furans; D013141:Spiro Compounds; C523374:cephalosporolide H; C520774:spiroketal; D015107:4-Butyrolactone