Abstract
The reactions of abamectin and ivermectin aglycones with equimolar quantities of acid chlorides, succinic anhydride (pyridine, DMAP), or aryl isocyanates (DCM, Et3N) at ambient temperature resulted in absolutely selective monoacylation of the OH group in position 5 (5-OH) of the macrocyclic skeleton and afforded the monoesters in 20–87 % yields. The reaction of the aglycones or their 5-monoesters with acid chlorides in a 1:2 M ratio (pyridine, DMAP, rt) afforded the diesters bearing identical or different acyloxy fragments in positions 5 and 13. Theoretical studies suggested that the higher reactivity of 5-OH compared to 13-OH is related to both thermodynamic and kinetic preference of the corresponding tetrahedral intermediate and transition state structures stabilized via an intramolecular hydrogen bond. 2009 Elsevier Ltd. All rights reserved.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
