Enantioselective Total Synthesis of the Unnatural and the Natural Stereoisomers of Vittatalactone

Abstract

The striped cucumber beetle, Acalymma vittatum, is a cause of major damage to cucurbit crops in North America. To develop an environmentally benign plant protection strategy, recent research has focused on identifying sex pheromones of the cucumber beetle. In this context, we developed the asymmetric total synthesis of the aggregation pheromone of A. vittatum, Vittatalactone, to determine its absolute configuration and to further examine the pheromone response in field studies. The synthesis features an enzyme-catalyzed approach toward the deoxypropionate structural motif. A preformed organocopper reagent could then be coupled in an enantioselective o-DPPB-directed allylic substitution with a functionalized o-DPPB-ester. By means of this efficient transformation, Vittatalactone could be obtained following a highly convergent synthetic process.

Enantioselective Total Synthesis of (+)‐Vittatalactone

“…Deprotection of acetonide 16 under acidic condition furnished the 1,3-diol 17 in 92 % yield for which the analytical data was in comparison with the data reported in the literature. [13] Selective oxidation of 1,3-diol 17 using TEMPO-BAIB afforded the β-hydroxy aldehyde, which was used as such in the next step without further purification for the oxidation of β-hydroxy aldehyde under Pinniks conditions (NaClO 2 , NaH 2 PO 4 ·2H 2 O) and furnished the β-hydroxy acid 18 in 76 % yield. [14] The NMR ( 1 H and 13 C) analysis and optical rotation [α] D = -7.6 of 18…”

“…[13] Eventual lactonization of β-hydroxy acid with p-toluenesulfonyl chloride in pyridine finally furnished the target natural product, (+)-vittatalactone in 78 % yield (Scheme 3).…”

“…13 C NMR spectra were recorded at 75 MHz in CDCl 3 using tetramethylsilane as a reference standard. Column chromatography was performed using silica gel (60-120 mesh) and the column was usually eluted with a mixture of ethyl acetate/petroleum ether.…”

Ozonolysis of Unsaturated Compounds in the Synthesis of Insect Pheromones and Juvenoids

“…A total asymmetric synthesis of the aggregation pheromone (vittatalactone) 317 of Acalymma vittatum, the principal grain and melon pest in North America, was proposed [95,96]. Key synthon 314 was obtained by repeating the reaction sequence of Cu-catalyzed allyl substitution to the corresponding syn-S N 2c products, their ozonolysis followed by borohydride reduction, bromination of the intermediate alcohols, conversion of bromides 312 and 313 to the Grignard reagents, and coupling of them with the corresponding ethers 311 and 318.…”

Towards the Synthesis of the 4,19‐Diol Derivative of (–)‐Mycothiazole: Synthesis of a Potential Key Intermediate

“…[7] Nevertheless, some methods have been published in the literature that give access to such a group, for example, by addition of a phenylboronic acid to an α-keto ester catalyzed by rhodium, [8] by addition of an alcohol to a vinyl epoxide in the presence of a catalytic amount of trialkylborane and palladium, [9] or by rearrangement of 2-(1-hydroxyalkyl)-1-cyclopropanols using organozinc catalysis. [10] The classical dihydroxylation of double bonds [11] or reduction of hydroxy esters [12] can also be used. Other 1,1-dialkyl-1,2-ethanediol intermediates have also been reported in the total syntheses of natural products, but they are obtained by tedious, not straightforward methods.…”