Picolylamine as an organocatalyst template for highly diastereo- and enantioselective aqueous aldol reactions

In vivo glucose-6-phosphatase inhibitory, toxicity and antidiabetic potentials of 2-picolylamine thioureas in Swiss albino mice

The 2-picolylamine is a simplest analogue of the alkaloid that has secondary and tertiary nitrogen function in its cyclic structure like that of alkaloids that can be derivatized to a number of biologically active compounds. In connection to our previous work, in the present work, three thiourea derivatives (I = 1,3-bis(2-benzyl-3-phenyl-1-(pyridine-2-yl) propyl) thiourea, II = 1,3-bis (pyridin-2-ylmethyl) thiourea, and III = 1-(2-benzyl-3-phenyl-1-(pyridine-2-yl) propyl)-3-phenylthiourea) were synthesized using 2-picolylamine template which is a readily available synthetic analogue of naturally occurring alkaloid. The biological effect of the synthesized derivatives were monitored on the activity of glucose-6-phosphatase in Swiss albino mice (21-days). The derivatives were also tested for their potential toxicity in a 28-days sub-chronic toxicity studies by assessing their effects on different parameters like hematological, serum biochemistry and liver histology. The therapeutic effect of the safe derivative (I) was examined in streptozotocin-induced diabetic mice as well. The derivatives showed inhibition of the enzyme activity from good to an excellent degree. Compound I had the highest inhibition with 21.42 ± 5.113 mg of the released phosphate as compared to that of the positive control group (84.55 ± 3.213 mg). Only I turned out to be safe for use in animals without exerting any toxic or lethal effects on any of the assessed parameters in the used animal model. Compound I efficiently reversed the effects like hyperglycemia, hyperlipidemia and weight loss in the test animals. Out of these three-tested compounds, I was found safe to be use as therapeutic agent in diabetes complications. However, further toxicological studies in other animal models are needed as well.

A Zn(II)-Coordination Polymer for the Instantaneous Cleavage of Csp3-Csp3 Bond and Simultaneous Reduction of Ketone to Alcohol

Two coordination polymers of Zn(II) and Cu(II) with n-butylmalonic acid have been achieved in this work. The crystallographic structural descriptions along with the sedimentary rock-type microstructural morphology of these two coordination polymers (CPs) have been explored. The reactivity of β-hydroxy ketones with these two CPs has also been investigated. The Zn(II)-CP shows a specific reactivity with β-hydroxy ketone at room temperature and in open air conditions. Through a microcolumn-based filtration technique, the Zn(II)-CP shows the capability to break the C_sp³-C_sp³ σ bonds of β-hydroxy ketone and simultaneously reduce the associated ketone to alcohol. Such conversion has been progressed without the use of any additional external reducing agent and any chemical workup or column chromatographic purification protocol. Other similar type CPs of Cu(II) and Mn(II) with n-butylmalonic acid completely failed to show similar reactivity with β-hydroxy ketone. On the basis of much experimental evidence, the most possible mechanistic pathway of the reactivity between β-hydroxy ketone and Zn(II)-CP has also been proposed through this work.

Enzyme Inhibitory, Antioxidant And Antibacterial Potentials Of Synthetic Symmetrical And Unsymmetrical Thioureas

Background

In this study, 2 symmetrical and 3 unsymmetrical thioureas were synthesized to evaluate their antioxidant, antibacterial, antidiabetic, and anticholinesterase potentials.

Methods

The symmetrical thioureas were synthesized in aqueous media in the presence of sunlight, using amines and CS₂ as starting material. The unsymmetrical thioureas were synthesized using amines as a nucleophile to attack the phenyl isothiocyanate (electrophile). The structures of synthesized compounds were confirmed through H¹ NMR. The antioxidant potential was determined using DPPH and ABTS assays. The inhibition of glucose-6-phosphatase, alpha amylase, and alpha glucosidase by synthesized compounds was used as an indication of antidiabetic potential. Anticholinesterase potential was determined from the inhibition of acetylcholinesterase and butyrylcholinesterase by the synthesized compounds.

Results

The highest inhibition of glucose-6-phosphatase was shown by compound V (03.12 mg of phosphate released). Alpha amylase was most potently inhibited by compound IV with IC₅₀ value of 62 µg/mL while alpha glucosidase by compound III with IC₅₀ value of 75 µg/mL. The enzymes, acetylcholinesterase, and butyrylcholinesterase were potently inhibited by compound III with IC₅₀ of 63 µg/mL and 80 µg/mL respectively. Against DPPH free radical, compound IV was more potent (IC₅₀ = 64 µg/mL) while ABTS was more potently scavenged by compound I with IC₅₀ of 66 µg/mL. The antibacterial spectrum of synthesized compounds was determined against Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Agrobacterium tumefaction and Proteus vulgaris). Compound I and compound II showed maximum activity against A. tumefaction with MIC values of 4.02 and 4.04 µg/mL respectively. Against P. vulgaris, compound V was more active (MIC = 8.94 µg/mL) while against S. aureus, compound IV was more potent with MIC of 4.03 µg/mL.

Conclusion

From the results, it was concluded that these compounds could be used as antibacterial, antioxidant, and antidiabetic agents. However, further in vivo studies are needed to determine the toxicological effect of these compounds in living bodies. The compounds also have potential to treat neurodegenerative diseases.

Catalytic enantioselective aldol reactions

Recent developments in catalytic asymmetric aldol reactions have been summarized.

Chiral picolylamines for Michael and aldol reactions: probing substrate boundaries

Here we report on inroads concerning increased substrate breadth via the picolylamine organocatalyst template, a vicinal chiral diamine based on a pyridine-primary amine motif. The addition of cyclohexanone to β-nitrostyrene has many catalyst solutions, but cyclopentanone and isobutyraldehyde additions continue to be challenging. PicAm-3 (10 mol%) readily allows the Michael addition of cyclopentanone or isobutyraldehyde (5.0 equiv.) to β-nitrostyrene derivatives. By contrast, PicAm-1 (7.0 mol%) is optimal for catalyzing the aldol reaction of cyclohexanone or cycloheptanone (3.3 equiv.) with aromatic aldehydes. Eighteen products are reported and for each reaction type new products are reported (4b-d, 9c). Very good yields and stereoselectivities are generally noted. The reactions, which require an acid additive, proceed via a transient chiral enamine and a mechanistic case is put forth for a bifunctional catalysis model.

2-Benzyl-3-phenyl-1-(pyridin-2-yl)propan-1-one

Mol­ecules of the title compound, C₂₁H₁₉NO, assume an approximate propellar shape, with the three aromatic rings being nearly perpendicularly aligned with respect to the plane formed by the C atoms that are connected to the methine C atom [dihedral angles: pyridyl 79.82 (4)°, phenyl 80.12 (3)° and phenyl 86.93 (3)°].

Asymmetric syn-selective direct aldol reaction of protected hydroxyacetone catalyzed by primary amino acid derived bifunctional organocatalyst in the presence of water

A new series of water compatible primary-tertiary diamine catalysts derived from natural primary amino acids bearing a hydrophobic side chain have been synthesized. These new primary-tertiary diamine-Brønsted acid conjugates bifunctional organocatalysts efficiently catalyzes the asymmetric direct syn selective cross-aldol reaction of different protected hydroxyacetone with various aldehydes in high yield (94%) and high enantioselectivity (up to 97% ee of syn) and dr of 91 : 9 (syn/anti) under mild reaction conditions.