A novel conformationally restricted analogue of 3-methylaspartic acid via stereoselective methylation of chiral pyrrolidin-2-ones

Diversity-Oriented Syntheses of β-Substituted α-Amino γ-Lactam Peptide Mimics with Constrained Backbone and Side Chain Residues

α- N-(Fmoc)Amino-γ-lactam dipeptides with a variety of β-substituents were synthesized stereoselectively with minimal β-elimination by routes employing, respectively, Mitsunobu chemistry and cyclic sulfamidate nucleophilic ring opening from trans- and cis-β-hydroxy-α-amino-γ-lactam precursors. This diversity-oriented method provides stereochemically pure dipeptide mimics bearing Cys, Ser, Thr, Dap, Dab, His, and other amino acid residues with constrained backbone and side chain conformations.

Bioactivities of a New Pyrrolidine Alkaloid from the Root Barks of Orixa japonica

A new pyrrolidine alkaloid named (Z)-3-(4-hydroxybenzylidene)-4-(4-hydroxyphenyl)-1-methylpyrrolidin-2-one was isolated from the ethanol extract of the root barks of Orixa japonica. The structure of the new alkaloid was elucidated on the basis of NMR and MS analysis. The compound exhibited larvicidal activity against the fourth instar larvae of Aedes aegypti (LC₅₀ = 232.09 μg/mL), Anopheles sinensis (LC₅₀ = 49.91 μg/mL), and Culex pipiens pallens (LC₅₀ = 161.10 μg/mL). The new alkaloid also possessed nematicidal activity against Bursaphelenchus xylophilus (LC₅₀ = 391.50 μg/mL) and Meloidogynein congnita (LC₅₀ = 134.51 μg/mL). The results indicate that the crude ethanol extract of O. japonica root barks and its isolated pyrrolidine alkaloid have potential for development into natural larvicides and nematicides.

β-Peptoids: synthesis of a novel dimer having a fully extended conformation

Chiral imines 1a,b, already synthesized in our laboratory, were converted in good yield by reduction into the corresponding N-benzyl-γ-lactams 2a,b. Desilylation followed by oxidation of the hydroxymethyl functionality gave the N-benzyl-β-amino acids 5a,b in good yield and high purity. Starting from compound 6a, the corresponding β-peptoid dimer 8 was prepared, together with its derivatives 9 and 10, these latter displaying conformational restriction about the peptide bond, as evidenced by NMR data.

Two new compounds from Dictamnus dasycarpus

Two new compounds, one new pyrrolidine alkaloid and one new eudesmane-type sesquiterpene derivative, named, respectively, as dictamnaindiol and dictamnadiol, were isolated from the EtOAc soluble fraction of the ethanolic extract from the root barks of Dictamnus dasycarpus. Their structures were elucidated as (3α,4β)-3-(6-ethoxy-6-(4-hydroxyphenyl)methyl)-4-(4-hydroxyphenyl)-1-methyl-pyrrolidin-2-one (1) and (1R, 4S, 7S, 10R)-1,11-dihydroxyl-4,14-epoxy-5(6)-eudesmene (2) on the basis of their spectral and chemical analysis.