Hemi-synthesis of novel chiral benzodiazepine derivatives from Eucalyptus citriodora essential oil: 2D NMR experiments and differential scanning calorimetry study of diastereoisomers

An efficient in situ condensation of citronellal, the main constituent of Eucalyptus citriodora essential oil (51%), with different amine derivatives of 2,3-diaminomaleonitrile and 3-[(2-aminoaryl)amino]dimedone has led to novel chiral benzodiazepine structures. All reactions were precipitated in ethanol and pure products were obtained in good yields (58-75%) without any purification. The synthesized benezodiazepines were characterized by spectroscopic techniques, namely 1H-NMR, 13C-NMR, 2D NMR and FTIR. Differential Scanning Calorimetry (DSC) and HPLC were used to confirm the formation diastereomeric mixtures of benzodiazepine derivatives.

Asymmetric Synthesis of Both Enantiomers of Dimethyl 2-Methylsuccinate by the Ene-Reductase-Catalyzed Reduction at High Substrate Concentration

Chiral dimethyl 2-methylsuccinate (1) is a very important building block for the manufacturing of many active pharmaceutical ingredients and fine chemicals. The asymmetric reduction of C=C double bond of dimethyl citraconate (2), dimethyl mesaconate (3) or dimethyl itaconate (4) by ene-reductases (ERs) represents an attractive straightforward approach, but lack of high-performance ERs, especially (S)-selective ones, has limited implementing this method to prepare the optically pure dimethyl 2-methylsuccinate. Herein, three ERs (Bac-OYE1 from Bacillus sp., SeER from Saccharomyces eubayanus and AfER from Aspergillus flavus) with high substrate tolerance and stereoselectivity towards 2, 3 and 4 have been identified. Up to 500 mM of 3 was converted to (S)-dimethyl 2-methylsuccinate ((S)-1) by SeER in high yields (80%) and enantioselectivity (98% ee), and 700 mM of 2 and 400 mM of 4 were converted to (R)-1 by Bac-OYE1 and AfER, respectively, in high yields (86% and 77%) with excellent enantioselectivity (99% ee). The reductions of diethyl citraconate (5), diethyl mesaconate (6) and diethyl itaconate (7) were also tested with the three ERs. Although up to 500 mM of 5 was completely converted to (R)-diethyl 2-methylsuccinate ((R)-8) by Bac-OYE1 with excellent enantioselectivity (99% ee), the alcohol moiety of the esters had a great effect on the activity and enantioselectivity of ERs. This work provides an efficient methodology for the enantiocomplementary production of optically pure dimethyl 2-methylsuccinate from dimethyl itaconate and its isomers at high titer.

Synthesis of Naphthoquinone Derivatives: Menaquinones, Lipoquinones and Other Vitamin K Derivatives

Menaquinones are a class of isoprenoid molecules that have important roles in human biology and bacterial electron transport, and multiple methods have been developed for their synthesis. These compounds consist of a methylnaphthoquinone (MK) unit and an isoprene side chain, such as found in vitamin K₁ (phylloquinone), K₂, and other lipoquinones. The most common naturally occurring menaquinones contain multiple isoprene units and are very hydrophobic, rendering it difficult to evaluate the biological activity of these compounds in aqueous assays. One way to overcome this challenge has been the application of truncated MK-derivatives for their moderate solubility in water. The synthesis of such derivatives has been dominated by Friedel-Crafts alkylation with BF₃∙OEt₂. This attractive method occurs over two steps from commercially available starting materials, but it generally produces low yields and a mixture of isomers. In this review, we summarize reported syntheses of both truncated and naturally occurring MK-derivatives that encompass five different synthetic strategies: Nucleophilic ring methods, metal-mediated reactions, electrophilic ring methods, pericyclic reactions, and homologation and side chain extensions. The advantages and disadvantages of each method are discussed, identifying methods with a focus on high yields, regioselectivity, and stereochemistry leading to a detailed overview of the reported chemistry available for preparation of these compounds.

Enantioselective Synthesis and Activity of All Diastereoisomers of ( E)-Phytal, a Pheromone Component of the Moroccan Locust, Dociostaurus maroccanus

The Moroccan locust, Dociostaurus maroccanus (Thunberg, 1815) (Orthoptera: Acrididae), is a polyphagous pest capable of inflicting large losses in agriculture under favorable environmental and climatic conditions. Currently, control of the pest relies solely on the application of conventional insecticides that have negative effects on the environment and human safety. In the search for a more rational, environmentally acceptable approach for locust control, we have previously reported that ( Z/ E)-phytal (1) is a male-produced candidate sex pheromone of this acridid. This molecule, with two stereogenic centers at C-7 and C-11, has four different diastereomers along with the Z/ E stereochemistry of the double bond at C-2. In this paper, we present for the first time the enantioselective synthesis of the four diastereomers of ( E)-phytal and their electrophysiological and behavioral activity on males and females. Our results demonstrate that the ( R, R)-phytal is the most active diastereomer in both assays, significantly attracting females in a double-choice Y olfactometer, and confirming the previous chromatographic assignment as component of the sex pheromone of the Moroccan locust.

A convenient and asymmetric protocol for the synthesis of natural products containing chiral alkyl chains via Zr-catalyzed asymmetric carboalumination of alkenes. Synthesis of phytol and vitamins E and K

[reaction: see text]. A convenient and asymmetric protocol for the synthesis of chiral oligoisoprenoids is described. Typically, a C14 vitamin E side chain 5 was synthesized in 47% yield over four steps. Isomeric purity of 5 was upgraded to >99% R at C-2 and 97% R at C-6 by the statistical formation of stereoisomeric p-phenylenebisurethanes and their diastereomeric separation. In addition, phytol and vitamin K were synthesized in 21% and 28% overall yields, respectively, over five steps from 1.