Synthesis of cyclic ethers and their utility in the synthesis of terpenoid compounds

Synthesis of some tricyclic ethers is described along with the methods developed to realize their transformation to diterpenoid compounds such as erythroxydiol-X (13), pimarane diterpenes, atisine (37), pisiferic acid (51) and carnosic dimethyl ether (76). Preparation of several bicyclic ethers is described along with their utility in synthesizing many other compounds. For example, cyclic ether 100 has been found a versatile intermediate for the synthesis of acolamone (103) and junenol (101). Similarly, the synthesis of endesmadienes (111), (112) and (117) from the cyclic ether 105 is reported. A formal total synthesis of the frullanolide (122) achieved from the cyclic ether 105 is described. The utilization of cyclic ether 135 in developing a formal total synthesis of glutinosone (142) is presented. The development of newer methods for the synthesis of cyclic ethers to be utilized in obtaining several natural and non-natural products is predicted.