Tritium labeling of avermectins B1a and B2a via stereoselective reduction of 5-ketoavermectins

Abstract

solvent program, at a flow rate of 1 mL/minute, was 5 min isocratic, 15 min linear increase in water from 0.5 to 1.4, and 20 min isocratic at the final solvent composition of 6:8:1.4. We achieved excellent separation (Figures 1 and 2) in 10 min less time beginning with a solvent composition of 6:8:0.5 and running a linear increase in water to a final composition of 6:8:1.5, flow rate 1.5 mL/min.The methods for phospholipids of red blood cell ghosts and squid axions did not separate sufficient quantities for further analysis. The data in Table I show that our method separates sufficient quantities of the phospholipids

The preparation of isotopically labelled macrocyclic compounds by organic synthesis

“…3 Molecular models of the respective ketone precursors suggested that tritide reduction of the less hindered alpha face would afford mostly the desired isomers and this proved to be the case. These labelled products were needed to clarify the mode of avermectin biological action thought to be the selective blockade of gamma-aminobutyric acid mediated neurotransmission.…”

“…3 H] Dihydrotacrolimus could be HPLC purified to homogeneity by this method and characterized by mass spectral analysis as well as 3 H NMR. With a specific activity in excess of 80 Ci/mmol, its 3 H NMR afforded a pattern characteristic of a tritiated propyl side chain 13 and the product was used to further elucidate the tacrolimus binding site.…”

“…With a specific activity in excess of 80 Ci/mmol, its 3 H NMR afforded a pattern characteristic of a tritiated propyl side chain 13 and the product was used to further elucidate the tacrolimus binding site.…”

“…Apparently, the high specific activity of 129 Ci/mmol was a key factor in the chromatographic separation. 70 In an analogous fashion, the related cyclic peptide [Nmethyl- 3 H] JES 1798 (6 above) was prepared soon afterward by the same group. 71 These labelled compounds were used for receptor binding studies to characterize their mode of action.…”

“…Clearly, some overlap has occurred, and on occasion the placement of certain compounds is somewhat arbitrary. Within each section, the order of discussion typically proceeds through isotopes of increasing atomic weight ( 2 H, 3 H, 13 C, 14 C, etc.) and references are usually arranged from earliest to latest unless the juxtaposition of certain related citations was more appropriate.…”