this method include the use of chiral phosphoric acids for the selective synthesis of
mono-anomeric spiroacetals [75, 76] and an intramolecular oxymercuration/reduction sequence [77, 78].
2.4.1 Acid-catalyzed Cyclizations
Fuwa and Sasaki [72, 73] have used this approach in their syntheses of attenol A 97
and the spiroacetal portion of didemnaketal B 106 (Scheme 27). En route to
Scheme 27 Fuwa and Sasaki’s syntheses of attenol A and didemnaketal B spiroacetal [72, 73]
Synthesis of 5,6- and 6,6-Spirocyclic Compounds
209