Iodine-Catalyzed Highly Diastereoselective Synthesis of trans-2,6-Disubstituted-3,4-Dihydropyrans: Application to Concise Construction of C28-C37 Bicyclic Core of (+)-Sorangicin A

• Published in: Chemistry : a European journal 2010-02, Vol.16 (7), p.2072-2078
• Main Authors: Mohapatra, Debendra K., Das, Pragna P., Pattanayak, Manas Ranjan, Yadav, J. S.
• Format: Article
• Language: English
• Subjects: Aminoglycosides - chemical synthesis; Aminoglycosides - chemistry; asymmetric synthesis; Bridged Bicyclo Compounds - chemical synthesis; Bridged Bicyclo Compounds - chemistry; Catalysis; Cyclization; iodine; Iodine - chemistry; Molecular Structure; oxygen heterocycles; Pyrans - chemical synthesis; Pyrans - chemistry; sorangicin A; Stereoisomerism
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200902999

A novel iodine‐catalyzed highly diastereoselective synthesis of trans‐2,6‐disubstituted‐3,4‐dihydropyrans have been achieved from δ‐hydroxy α,β‐unsaturated aldehydes by treating with allyltrimethyl silane in THF at room temperature with good to excellent yields. This methodology has been successfully implemented for a concise asymmetric synthesis of C28–C37 dioxabicyclo[3.2.1]octane ring system of (+)‐sorangicin A in 8 steps with 21 % overall yield. Double iodocyclization: An iodine‐catalyzed cyclization that led to exclusive formation of trans‐2,6‐disubstituted‐3,4‐dihydropyrans is described. A second iodo‐cyclization has been carried out for an efficient and concise synthesis of novel C28–C37 bicyclic core of (+)‐sorangicin A in 8 steps with 21 % overall yield (see scheme).