Synthesis Mediated by Ring-Closing Metathesis – Applications in the Synthesis of Azasugars and Alkaloids

Abstract

The application of the ring-closing metathesis (RCM) castanospermine (5) is presented. The utilisation of two RCM steps in the synthetic sequence leading to the multicyclic reaction to the construction of a wide variety of nitrogencontaining ring systems is described. The examples include ABCDE nucleus 7 of the complex alkaloid manzamine A (6) is discussed. pyrrolizidine, indolizidine, and quinolizidine derivatives related to azasugars. A formal total synthesis of

Total Synthesis of (±)‐Haliclonacyclamine C

“…Iminium salt 1.67 is almost identical to intermediate 1. 58 in the propsed biosynthesis of sarain A (1.5).…”

Total Synthesis of (±)‐Haliclonacyclamine C

“…[53][54][55][56][57][58] By utilizing an intramolecular Diels-Alder strategy they were able to not only form the tricycle, but set three chiral centers in a single step (Scheme 27). 6 They constructed the unsaturated 13-membered ring using a ring closing metathesis reaction.…”

Synthetic Studies of Natural 10-Membered Lactones, Mueggelone, Microcarpalide, and Sch 642305, Which Have Interesting Bioactivities

“…44) They constructed the intermediate ent-18 by cross metathesis 4,19) of , -unsaturated ester 44 using 2nd-generation Grubbs catalyst 20) under ethylene, because direct methylenation of hemiacetal 43 (conversion to ent-18) was not successful, and RCM of , -unsaturated ester 44 did not proceed. 47) Hemiacetal 43 was synthesized from alcohol 41 and acid 42, whose stereocenters originated in Sharpless AD 30,31) and (S)-malic acid respectively. In their synthesis, installation of the second double bond for RCM was problematic and lowered synthetic efficiency.…”