A new cyclopeptide alkaloid from the bark of waltheria douradinha

Waltherine-C (5), a novel 14-membered cyclopeptide alkaloid has been isolated, together with four known cyclopeptide alkaloids, waltherine-A (1) and -B (2), scutianine-B (3) and adouetine-Y' (4), from the bark of Waltheria douradinha (Sterculiaceae) from Rio Grande do Sul, Brazil. The structure and NMR assignments of this new alkaloid were determined by 1D and 2D NMR techniques. The stereochemistry of the ring amino acid residue and the N,N-dimethyl amino acid side-chain has been assigned by gas chromatography employing modified cyclodextrins as chiral stationary phases.     

Haloacetylated enol ethers. 14 [6]. Reaction of β-alkoxyvinyl trifluoromethyl ketones with N-methylhydroxylamine

The reaction of a series of β-methoxyvinyl trifluoromethyl ketones [CF₃COC(R²)?C(OMe)R¹, where R¹ = Me, -(CH₂)₃-C3, -CH₂)₄-C3, Ph and R² = H, Me, -(CH₂)₃-C4, -(CH₂)₄-C4] with N-methylhydroxylamine is reported. The regiochemistry of the reaction are explained by MO calculation data.     

Convenient synthesis of 3-aminomethylenedihydrofuran-2-ones

A simple and convenient synthesis of a series of 3-aminomethylenedihydrofuran-2-ones from the reaction of 3-trichloroacetyl-4,5-dihydrofuran with amines, is presented.     

Synthesis and structural study of a new series of 2‐methylsulfanyl‐tetrahydropyrimidines from β‐alkoxyvinyl trihalomethyl ketones

This work describes the synthesis of a novel series of 2‐methylsulfanyl‐tetrahydropyrimidines, from the cyclocondensation reaction of β‐alkoxyvinyl trihalomethyl ketones with 2‐methyl‐2‐thiopseudourea sulfate, in good yields. A detailed ¹H‐ and ¹³C‐NMR study was performed on the 2‐methylsulfanyl‐tetrahydropyrimidines obtained and 3D structures were proposed based on AM1 calculations supported by ¹H NMR coupling constants and NOESY experiments.     

An ionic liquid as reaction medium for the synthesis of halo-containing β-enaminones at room temperature

A series of twenty halomethylated β-enaminones [RC(O)CH=C(R ¹)NR ³ R ⁴, where R = CF₃,CCl₃, CHCl₂; R ¹ = H, Me, Ph; R ³ = H, Me, Bu, Et; R ⁴ = Me, Et, Bu, allyl, tert-amyl, CH₂CH₂OH, Bn, Ph] were synthesized using the ionic liquid [bmim]BF₄ at room temperature. It is demonstrated that this ionic liquid is a reaction medium suitable for the amination of β-alkoxyvinyl halomethyl ketones. The advantages of this method are the absence of solvents, short reaction times, and good yields. Correspondence: Marcos A. P. Martins, Núcleo de Química de Heterociclos – NUQUIMHE, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil.