Synthesis and Use of Stereospecifically Deuterated Analogues of Palmitic Acid To Investigate the Stereochemical Course of the Δ¹¹ Desaturase of the Processionary Moth

Abstract

Thaumetopoea pityocampa pheromone glands contain desaturases that, after several sequential reactions from palmitic acid, catalyze the formation of a unique enyne fatty acid, which is the immediate sex pheromone precursor. In this article, we describe the synthesis of different stereospecifically deuterium-labeled and isotopically tagged palmitic acid probes needed to decipher the stereochemical course of the T. pityocampa Delta(11) desaturase. The synthesis of probes has been carried out by a chemoenzymatic route, in which the key step is the kinetic lipase-catalyzed resolution of racemic mixtures of secondary propargyl alcohols. The presence of the acetylenic bond simplifies the absolute configuration determination of the resolved alcohols. Moreover, it allows the introduction of the isotopic tag by deuteration. By use of the probes thus prepared, experimental evidence is presented that the Delta(11) desaturase of T. pityocampa transforms palmitic acid into (Z)-11-hexadecenoic acid by removal of the pro-(R)-hydrogen atoms from both C11 and C12.

A multifunctional desaturase involved in the biosynthesis of the processionary moth sex pheromone

“…Experiments with mass labeled substrates demonstrated that all of the three reactions performed by Tpi-PGFAD begin with oxidation of the carbon atom located nearest the carboxylate end: C11 in ⌬ 11 desaturation and acetylenation (35,36) and C13 in ⌬ 13 desaturation (37). Because a triple bond is shorter (1.21 Å) than a single bond (1.55 Å), accommodation of the ⌬ 11 desaturase substrates in the enzyme active site sets C11 accessible to the iron oxidating function, whereas accommodation of 11-hexadecynoic acid leaves C13 better positioned for initial oxidation.…”

Synthesis of ceramides NS and NP with perdeuterated and specifically ω deuterated N‐acyl residues

“…For that, the corresponding alcohols were oxidized in a different mode. The oxidation with pyridinium dichromate seems to be a very mild method, and therefore, we tested this reaction . However, as a result of this procedure, we found a peak indicating the loss of 1 CH 2 group in the mass spectrum.…”

(ω‐2,ω‐2,ω‐3,ω‐3)‐Tetradeuterio‐fatty acids for mechanistic studies of enzyme‐catalyzed hydroxylation reactions

“…The concept is to prepare a short labeled alcohol, 4,4,5,5-tetradeuterioheptan-1-ol, that can be converted to a tosylate that is used to alkylate an (o-1)-alkyn-1-ol tetrahydropyranyl (THP) ether of any length. Similar approaches involving termination of alkyne alkylation followed by reduction of the alkyne with deuterium gas or alkylation of an alkyne with a deuterated iodoalkane followed by reduction with hydrogen gas have been reported, [5][6][7][8][9] but we are not aware of its use for the longer chain fatty acids we prepared in this work. The 1-alkyn-o-ols are either commercially available or prepared from 4-pentyn-1-ol by alkylation of the protected alcohol and base-catalyzed isomerization of the alkynyl group from an internal position to the terminal o-1 position.…”