Asymmetric Organocatalytic One-Pot, Two-Step Sequential Process to Synthesize Chiral Acetal-Containing Polycyclic Derivatives from Cyclic Hemiacetals and Enones.

We have developed an efficient one-pot, two-step sequential process to synthesize biologically and synthetically important chiral acetal-containing polycyclic derivatives. This novel protocol had been proved to proceed via Michael-lactolization-oxocarbenium ion ring-closing sequence, which was initiated by a key reactive enamine intermediate and interrupted the previously established reaction pathway of two different enones used in this work, and generated the corresponding cycloadducts with excellent stereoselectivity bearing up to seven continuous stereocenters. Both chiral and racemic starting cyclic hemiacetals worked well in this strategy. The synthetic applications of the obtained polycyclic products have also been demonstrated.