Advances in the Asymmetric Synthesis of Bridged and Fused Bicyclic Acetals

Fused and bridged bicyclic acetals are important structural motifs found in a diverse array of biologically active molecules. These conformationally rigid but stable structural segments are established within natural and unnatural compounds with biological importance. The structural and biological features of the molecules containing the fused and bridged ring systems have triggered a profound impact in the layout of newer synthetic methodologies and other designed entities. The interest in the development of efficient strategies to construct bicyclic scaffolds with fused and bridged bicyclic acetals in a stereocontrolled manner is substantial and challenging in the community of synthetic chemistry. The purpose of this review is to shed some light on the intriguing chemistry involved in the synthesis of conformationally constrained bridged and fused bicyclic acetals and its exploitation towards the synthesis of complex natural and unnatural molecules of biological and synthetic interest. This review article highlights the asymmetric synthesis of conformationally rigid fused [x,y] and bridged [x.y.z] bicyclic acetals to construct complex natural and unnatural molecules of biological and synthetic interest. For these rigid molecular frameworks, the stereoselective cyclization and C–C bond formation has been widely explored.