Valentine Ragoussis

Synthesis of homoproline analogues containing heterocyclic rings and their activity as organocatalysts for Michael reaction

Two homoproline derivatives containing either the 5-thioxo-1,2,4-oxadiazole or the 2-oxo-1,2,3,5-oxathiodiazole bioisosteric groups, in replacement of the carboxyl group, were synthesized and their catalytic activities in Michael reactions were evaluated. The derivative containing the 5-thioxo-1,2,4-oxadiazole ring outperforms proline in the context of enantioselectivity in the reactions between β-nitrostyrene and acetone or cyclohexanone, indicating that the conversion of the carboxylic group of homoproline to a bioisosteric heterocyclic ring leads to a superior organocatalyst.

Improved total synthesis of (±)-drimenin

A highly efficient three-step synthesis of the sesquiterpene (±)-drimenin (4) from the β-keto ester (1) is described. Compound (1) was prepared in five steps from linalool.

Improved Synthesis of (3E,7Z)-3,7-Tetradecadienyl Acetate, the Major Sex Pheromone Constituent of the Potato Pest Symmetrischema tangolias (Gyen)

An efficient six-step synthesis of (3E,7Z)-3,7-tetradecadienyl acetate, the major component of the sex pheromone of the potato pest Symmetrischema tangolias (Gyen), is described, starting from the commercially available dihydropyran. The stereoselective formation of the 7Z double bond is accomplished by a Wittig reaction, while the 3E double bond is formed by a modified Knoevenagel condensation. The overall yield of the synthesis is 28%, giving the final product in high stereochemical purity (95%). The simplicity and the low cost of the herein reported synthesis suggest the potential practical use of the above pheromone in integrated management programs, for this serious insect pest.

A simple approach to the synthesis of muramic acid and isomuramic acid: 1H and 13C NMR characterisation

Abstract A simple and efficient synthesis of 2-amino-3- O -[( R )-1-carboxyethyl]-2-deoxy- d -glucose (muramic acid, 6 ) and its stereoisomer 2-amino-3- O -[( S )-1-carboxyethyl]-2-deoxy- d -glucose (isomuramic acid, 7 ) from methyl 2-acetamido-4,6- O -benzylidene-2-deoxy-α- d -glucopyranoside ( 1 ) is described. Condensation of the O-3 oxyanion of 1 with an excess of methyl ( R,S )-2-bromopropionate, followed by alkaline hydrolysis of the crude product and subsequent acidification, afforded crystalline methyl 2-acetamido-4,6- O -benzylidene-3- O -[( R,S )-1-carboxyethyl]-2-deoxy-α- d -glucopyranoside ( 2 ), in 72% yield, as a mixture of diastereomers. Esterification of 2 with an excess of diazomethane afforded quantitatively the corresponding mixture of epimeric esters, which were very easily separated by column chromatography on silica gel, giving pure ( R ) and ( S ) epimeric esters. Removal of the benzylidene and acetyl groups by acid hydrolysis gave, respectively, muramic acid ( 6 ), in 95% yield and isomuramic acid ( 7 ), in 93% yield. 1 H and 13 C NMR data are given.

Synthesis and resolution of albicanic acid. Simple access to optically active drimane sesquiterpenes

The synthesis of albicanic acid (±)-(2) and the resolution to its enantiomers (+)-(2) and (–)-(2) are described. Determination of their optical purity was by 1H n.m.r. spectroscopy of the corresponding methyl esters (+)-(1) and (–)-(1) with Eu(dcm)3. The absolute configuration of the acids (+)-(2) and (–)-(2) has been determined by transformation to their alcohols (–)-(5) and (+)-(5) and interrelation with the natural albicanol. An efficient formal total synthesis of both enantiomeric forms of three drimanic sesquiterpenes, drimenin (7), isodrimenin (8), and drim-7-ene-11,12-diol (9), presenting special synthetic interest, is reported, starting from the corresponding enantiomers of albicanic acid (2).

Formal total synthesis of (+)-12-deoxyscalarolide

An effective formal total synthesis of (+)-12-deoxyscalarolide is described, starting from natural manool. Two alternative reaction schemes have been investigated for the synthesis of the tetra-carbocyclic key intermediate (–)-methyl 17-oxo-24-norscalaran-25-oate. The unsaturated lactonic ring is then created from this ester in three steps to afford, in high yield, the (–)-scalar-16-en-25,24-olide which is easily isomerised under basic conditions to (+)-12-deoxyscalarolide.

1,5,7-Trioxaspiro[5.5]undecane, a pheromone analog with high biological activity for the olive fruit fly,Dacus oleae.

Abstractl,5,7-Trioxaspiro[5.5]undecane, an analog of the major sex pheromone (olean) of the olive fruit fly, was synthesized via two different routes and tested for biological activity under laboratory and field conditions. In laboratory tests, its activity was comparable to that of olean, especially when a stabilizer or a high concentration was used. In field tests, its activity reached the level of olean only when a stabilizer and an open-type dispenser, which allows high rates of evaporation, were used. The residual activity of the analog dispensers did not exceed two weeks both under laboratory and field conditions compared to over four months for olean.

Determination of natural olive fruit fly pheromone in insect samples by enzyme linked immunoassays

The olive fruit fly pheromone avidin-biotin ELISA immunoassay, based on the use of polyclonal G antibodies derived from rabbits (reported previously) and a newer assay, based on the use of polyclonal Y antibodies isolated from the eggs of laying hens (reported in this paper), were applied successfully for the analysis of natural pheromone in virgin adult female olive fruit flies. According to the results obtained, the pheromone content in the glands of adult female olive fruit flies increases from the third to the ninth day of their age. During the calling period, the female olive fruit flies seem to emit approximately 1.1microg pheromone/insect/day at least. The immunoassay, based on the Y antibodies, is slightly more sensitive (detection limit 40ng/mL) than the assay based on polyclonal anti-pheromone rabbit antiserum (detection limit 80ng/mL). As revealed by thorough cross-reactivity studies, including 14 structurally similar to the olive fruit fly pheromone molecules, the newer immunoassay is less selective than the previous one and seems to cross react with few molecules bearing the spiroketal moiety.

A Short and Efficient Synthesis of 2-Methyltetrahydrofuran-3-One

Abstract 2-Methyltetrahydrofuran-3-one (3), a volatile constituent of the aroma complex of roasted coffee, is efficiently prepared in satisfactory yield (55,2%) by oxidative hydroxylation of the 2-acetylbutyrolactone (4).