R. F. Talipov

SULFUR-CONTAINING DERIVATIVES OF MONO- AND BICYCLIC NATURAL MONOTERPENOIDS

Examples of thiylation of natural mono- and bicyclic and variously functionalized monoterpenoids (alkenes, ketones, epoxides, alcohols) and the latest transformation pathways of the newly formed sulfur-containing derivatives were reviewed.

Catalyzed synthesis of β-amino acids esters

β-Aminoalcohols, β-amino acids, and their esters exhibit a wide range of biological action antitumor, immunostimulating, antiphlogistic). They are used as peptidomimetics and are precursors of many synthetic and natural compounds, in particular, of β-lactams [1– 4]. For instance, bestatin, [(2S,3R)-3-amino-2-hydroxy4-phenylbutanoyl]-L-leucine, is a specific inhibitor of the chemotoxic activity of the aminopeptidase possessing a low toxicity; it is used in medical practice as immunomodulator and antitumor drug [1]. The intense studies on the development of new methods for preparation the mentioned compounds are going on, and the substances as a rule are obtained by the nucleophilic Michael addition of primary or secondary amines to the activated C=C bond [5, 6]. The reaction is commonly performed in polar solvents (alcohols or carboxylic acids), the process is carried out in the presence of catalysts, Lewis acids (AlCl3, TiCl4, SnCl4) that accelerate Michael reaction [2, 5–10]. Recently as catalysts triflates of lanthanides were suggested [6]. However even at the use of new more efficient catalysts the reaction often proceeds nonselectively and requires several hours at 50–100°C and the presence of organic solvents. Therefore the development of catalytic methods free of the mentioned drawbacks is an urgent task. We report here on the new convenient catalytic procedure for one-stage preparation of β-amino acids esters by the reaction of esters of conjugated unsaturated acid with a series of primary and secondary amines in the presence of Kuganak montmorillonite Al2O3 . 4SiO2 . 2H2O that contains relatively high amount of TiO2. As esters of α,β-unsaturated acids we used methyl acrylate (Ia), allyl acrylate (Ib), methyl methacrylate (Ic), and dimethyl maleate (Id), and as amines, isopropylamine (IIa), butylamine (IIb), benzylamine (IIc), monoethanolamine (IId), diethylamine (IIe), and morpholine (IIf). The experiments were carried out at 20°C over 0.5 and 1.5 h at molar ratio of the α,β-un-saturated acid–amine 2 : 3.

(R)-4-Menthenone in the synthesis of optically pure sex pheromone of the peach leafminer moth (Lyonetia clerkella)

The synthesis of (14S)-methyloctadec-1-ene, sex pheromone of the peach leafminer moth (Lyonetia clerkella), is described to demonstrate a new potential of the synthetic use of (R)-4-menthenone.

Theoretical investigation of the role of formaldehyde dimers in the Prins reaction

Some features of adding a formaldehyde dimer to alkenes by the Prins reaction with the formation of oxygen-containing heterocycles are studied at the MP2(fc)/6-31G(d) computational level. The structure of the transition states and key intermediates are established, and thermochemical reaction parameters are determined. It is shown that this interaction in the gas phase or nonpolar media with the formation of 1,3-dioxanes is a single-stage pseudo synchronous syn-addition. Alkyl substituents at the double bond reduce activation energy. It is revealed that the hydrogenated pyrans formation by the Prins reaction is possible not only with the participation of formaldehyde monomers, but with its oligomers either. However, the activation energy of this reaction is higher than that of 1,3-dioxane formation.

Reactions of (R)-4-Menthen-3-one with Aluminum and Boron-Containing Hydrides

It was shown that the most effective and stereospecific hydride reductant for (R)-4-menthen-3-one to (1R,3R)-menthen-3-ol was i-Bu2AlH whereas the complex BH3·THF, which exhibited the same properties relative to the substrate carbonyl, was a regiospecific but relatively non-stereospecific hydroborating reagent of its double bond.

Natural cyclic α, β-enone monoterpenoids in nucleophilic addition reactions

The literature on transformations of natural cyclic α,β-enone monoterpenoids into compounds of more complicated structure via 1,2-and 1,4-addition reactions was reviewed. The data were systematized according to the effects of the conditions and nature of the starting substrates on the selectivity of the 1,2-and 1,4-addition reactions.

(R)-4-Menthen-3-one anti-Oxime and Its Transformation under Beckman Rearrangement Conditions

Abstract(R)-4-Menthenone anti-oxime was synthesized for the first time. Its transformations under Beckman rearrangement conditions were studied.

A theoretical investigation of the reaction mechanism for hydrogenated furan formation under Prins reaction conditions in trifluoroacetic acid medium

The formation mechanism of hydrogenated furans by coupling between terminal alkenes and aldehydes in trifluoroacetic acid medium were investigated by ab initio calculations, the main attention was focused on the study of the rate controlling step. Two possible mechanisms for this reaction involving unsaturated alkoxycarbenium ions or dioxolenium ions as a key intermediate were considered. It was shown that the mechanism of formation of 3-alkylsubstituted hydrogenated furans in trifluoroacetic acid under Prins reaction conditions preferably includes recyclization of 3-(2-hydroxyethyl)-1-trifluoromethyl-2,5-dioxolenium ions.

THIYLATION OF (R)-4-MENTHEN-3-ONE AND ITS DERIVATIVES

Thiylation of (R)-4-menthen-3-one and its derivatives was studied. New sulfides and sulfoxides of the menthane series were synthesized.

Separation of a mixture of R-menth-4-en-3-one and (−)-menthone

A promising chiral synthon is R-menth-4-en-3-one (1) [1-4], which is produced from the natural monoterpenoid l-menthol through the intermediate (-)-menthone (2) [5, 6] and is often contaminated (up to 10%) with the latter. The usual purification methods, including chromatographic ones, do not produce 1 of the desired purity. It is known [7] that 2 does not form bisulfites. Therefore, we supposed that it might be possible to isolate 1 from a mixture with 2 by forming the bisulfite derivative (3) of the carbonyl. According to our previous research [1], nucleophilic addition to 1 should occur via 1,2-addition to the carbonyl. Furthermore, the reaction was performed under the literature conditions [8, 9] in order to prevent 1,4-addition of NaHSO3.