Structures and Total Syntheses of the Plecomacrolides

The plecomacrolides are a large family of natural products typically featured with a 16- or 18- membered macrolactone possessing two conjugated diene units and a hemiacetal side chain. The macrocycle skeleton is connected with the side chain through a three-carbon linker, forming a biologically important intramolecular hydrogen bonding network among the lactone/linker/hemiacetal structural motif. Many members of the plecomacrolides act as selective inhibitors of vacuolar H+-ATPases (V-ATPases) and they are considered to have the potential for treatment of postmenopausal osteoporosis. Significant progress has been achieved in recent years in the area of plecomacrolide total synthesis. These include the total synthesis of bafilomycin A1 by Evans, Toshima, Hanessian, and Roush, of bafilomycin V1 by Marshall, of hygrolidin by Hashimoto and Yonemitsu, of concanamycin F by Paterson and Toshima, and of formamicin by Roush. The synthetic strategies and key transformations used in the total synthesis are discussed.