A Cascade “Prins-Pinacol-Type Rearrangement and C4-OBn Participation” on Carbohydrate Substrates: Synthesis of Bridged Tricyclic Ketals, Annulated Sugars and C2-Branched Heptoses

Tandem Prins cyclizations for the construction of oxygen containing heterocycles

Tandem Prins cyclization is a versatile method for the synthesis of fused/bridged/spirotetrahydropyran scaffolds. Therefore, it has become a powerful tool for the stereoselective synthesis of oxygen/nitrogen containing heterocycles. Indeed, previous review articles on Prins spirocyclization illustrate the synthesis of spirotetrahydropyran derivatives and the aza-Prins reaction demonstrates its application in the total synthesis of natural products. The current review is devoted specifically to highlight tandem Prins cyclizations for the construction of fused scaffolds and related frameworks with a particular emphasis on recent applications. The mechanistic aspects and the scope of the methods are briefly discussed herein.

Stereoselective synthesis of sugar-fused (or 1,2-annulated) isochromans and isochromanones by using oxa-Pictet-Spengler reaction

A highly efficient stereoselective synthesis of sugar fused 1,2-annulated isochromans is reported by utilizing the oxa-Pictet-Spengler cyclization reaction. The process is found to be very general as both glucal and galactal derived C2-hydroxy-α-C-aryl glycosides lead to the target molecules in good yields. The utility of this strategy was extended to the synthesis of sugar fused isochromanones, which are bergenin type molecules.

Stereoselective synthesis of 2-deoxy-β-C-aryl/alkyl glycosides using Prins cyclization: Application in the synthesis of C-disaccharides and differently protected C-aryl glycosides

2-Deoxy-β-C-aryl/alkyl glycosides were synthesized from di-O-pivaloyl protected homoallylic alcohol derived from D-mannitol with various aldehydes via the Prins cyclization. The salient features of this methodology are high yields and excellent stereoselectivity. This method has also been successfully applied to the synthesis of differently protected 2-deoxy-β-C-aryl glycosides and C-disaccharides. One of the 2-deoxy-β-C-aryl glycosides was utilized as a glycosyl acceptor in the glycosylation to synthesize an O-linked disaccharides.