DISPIROKETALS IN SYNTHESIS .10 - FURTHER REACTIONS OF DISPOKE PROTECTED LACTATE AND GLYCOLATE ENOLATES

alpha-Hydroxy acids have been reacted with bis-dihydropyrans to give d ispiroketal adducts 13,16-tetraoxadispiro[5.0.5.4]-hexadecan-14-ones). The enolates derived from these compound undergo reaction with electr ophiles with generally high levels of diastereoselectivity. Subsequent deprotection of these compounds gives alpha-hydroxy esters of high en antiomeric excess.