Secondary–secondary diamine catalysts for the enantioselective Michael addition of cyclic ketones to nitroalkenes

Organocatalytic Asymmetric Michael Addition of Ketones to α, β-Unsaturated Nitro Compounds

An organic catalyst “(R, R)-1,2-diphenylethylenediamine(DPEN) derivative’’ was devel-oped as a chiral bifunctional organocatalyst and applied for asymmetric Michael additions of aromatic ketones to trans-β-nitroalkene compounds under neutral conditions. The isopropyl-subs-tituted thiourea catalyst in neutral condition provides high chemical yield and enantioselectivities (ee) (up to 96% yield, 98% ee).

The influence of chosen fungicides on the activity of aminopeptidases in winter oilseed rape during pods development

Cultivation of oilseed rape requires application of specific fungicides. Besides their protective role, they can potentially influence the expression and activity of crucial enzymes in the plant. Among the large number of enzymes expressed in plants, aminopeptidases play a key role in all crucial physiological processes during the whole life cycle (e.g. storage protein mobilization and thus supplying plant with needed amino acids, as well as plant aging, protection and defense responses). In the present paper, we evaluate for the first time, the influence of the treatment of winter oilseed rape with commercially available fungicides (Pictor 400 SC, Propulse 250 SE and Symetra 325 SC), on the activity of aminopeptidases expressed in each plant organ (flowers, leaves, stems and pods separately). Fungicides were applied once, at one of the three stages of oilseed rape development (BBCH 59-61, BBCH 63-65 and BBCH 67-69). The aminopeptidase activity was determined using six different amino acid p-nitroanilides as substrates. The results have shown, that in control plants, at the beginning of intensive pods development and seeds production, hydrophobic amino acids with bulky side chains (Phe, Leu) were preferentially hydrolysed. In control plants, the activity was ~3.5 times higher in stems and pods, compared to leaves. The treatment with all pesticides caused significant increase in aminopeptidases hydrolytic activity toward small amino acids Gly, Ala as well as proline, mostly in flowers and leaves. These amino acids are proven to be crucial in the mechanisms of delaying of plant aging, development of better resistance to stress and plant defense. It can be suggested, that studied fungicides enhance such mechanisms, by activating the expression of genes coding for aminopeptidases, which are active in hydrolysis of N-terminal amino acids such as Gly, Ala, Pro from storage peptides and proteins. Depending on fungicide, the major increase of aminopeptidase activity was observed after application at BBCH 67-69 (Pictor 400 SC and Symetra 325 SC) and BBCH 63-65 (Propulse 250 SE) stages of development. Our study revealed, that agrochemical treatment and time of application, influenced the expression and activity of aminopeptidases, even though they were not molecular targets of applied fungicides. Since aminopeptidases are widely distributed throughout all organisms and are crucial in many key physiological processes, it can be expected, that factors influencing their expression and activity in plants, can also influence these enzymes in other organisms, especially humans and other mammals.

An efficient and enantioselective Michael addition of aromatic oximes to α,β-unsaturated aldehydes promoted by a chiral diamine catalyst derived from α,α-diphenyl prolinol

Chiral diamine catalysts 11a-e derived from α,α-diphenyl prolinol were prepared and successfully applied to the Michael addition of aromatic oximes to α,β-unsaturated aldehydes in mediocre to good yields (up to 78%) and good to high enantioselectivities (up to 93% ee).

Stereoselective synthesis of 3-aryloctahydroindoles and application in a formal synthesis of (-)-pancracine

A stereoselective synthesis of 3-aryloctahydroindoles from enantiomerically enriched gamma-nitroketones has been developed. Reduction of imines derived form the nitroketones provides the trans-fused octhaydroindole motif selectively. The cis-octahydroindole skeleton is accessible by an invertive cyclization strategy involving a diastereomerically pure nitromesylate intermediate. This approach was employed in the synthesis of an advanced intermediate to (-)-pancracine. The gamma-nitroketone starting materials are readily available via an organocatalytic Michael reaction.