Asymmetric Dehydrative Cyclization of Allyl Alcohol to Cyclic Ether Using Chiral Brønsted Acid/CpRu(II) Hybrid Catalysts: A DFT Study of the Origin of Enantioselectivity.

To elucidate the reaction mechanism and the origin of the enantioselectivity of the asymmetric dehydrative cyclization of allyl alcohol to cyclic ether catalyzed by a Cp-ruthenium complex and a chiral pyridinecarboxylic acid, (R)-X-Naph-PyCOOH, density functional theory (DFT) calculations were performed. According to the DFT calculations, the rate-determining step is the dehydrative σ-allyl formation step with ΔG‡ = 18.1 kcal mol-1 at 80 °C. This agrees well with the experimental data (ΔG‡ = 19.01 kcal mol-1 at 80 °C). The DFT result showed that both hydrogen and halogen bonds play a key role in the high enantioselectivity by facilitating the major R,SRu-catalyzed reaction pathway via a σ-allyl Ru intermediate to generate the major (S)-product. In contrast, the reaction is sluggish in the presence of the diastereomeric R,RRu catalyst with an apparent activation energy of 33.1 kcal mol-1; the minor (R)-product is formed via a typical π-allyl Ru intermediate and via a minor pathway for the cyclization step. In addition, the calculated activation Gibbs free energies, 14.4 kcal mol-1 for I < 16.8 kcal mol-1 for Br < 18.1 kcal mol-1 for Cl, reproduced the observed halogen-dependent reactivity with the (R)-X-Naph-PyCOOH ligands. The origin of the halogen trend was clarified by a structural decomposition analysis.

Synthesis and biological evaluation of chemokine receptor ligands with 2-benzazepine scaffold.

Targeting CCR2 and CCR5 receptors is considered as promising concept for the development of novel antiinflammatory drugs. Herein, we present the development of the first probe-dependent positive allosteric modulator (PAM) of CCR5 receptors with a 2-benzazepine scaffold. Compound 14 (2-isobutyl-N-({[N-methyl-N-(tetrahydro-2H-pyran-4-yl)amino]methyl}phenyl)-1-oxo-2,3-dihydro-1H-2-benzazepine-4-carboxamide) activates the CCR5 receptor in a CCL4-dependent manner, but does not compete with [3H]TAK-779 binding at the CCR5. Furthermore, introduction of a p-tolyl moiety at 7-position of the 2-benzazepine scaffold turns the CCR5 PAM 14 into the selective CCR2 receptor antagonist 26b. The structure affinity and activity relationships presented here offer new insights into ligand recognition by CCR2 and CCR5 receptors.

Catalytic dehydrative S-allylation of cysteine-containing peptides in aqueous media toward lipopeptide chemistry.

Thiol-containing peptides and cysteine have been successfully S-allylated with various allyl alcohols in aqueous medium containing a catalytic amount of [CpRu(η(3)-C(3)H(5))(2-quinolinecarboxylato)]PF(6). Quick and easy install of 2-propen-l-ol having a long-chain alkyl group at C(2) facilitates the synthesis of a new series of artificial lipopeptides, indicating a potential application to synthetic biology.

Hyperkeratotic variant of porokeratosis Mibelli with dermal amyloid deposits.

We report a case of hyperkeratotic variant of porokeratosis Mibelli with dermal amyloid deposits. A 66-year-old man presented with multiple brownish keratotic lesions on the lower extremities, a verrucous nodule on the third toe of the left foot and brownish verrucous plaques on the buttocks for several years. Histopathological examination of the hyperkeratotic plaque in the right gluteal region revealed extreme hyperkeratosis and cornoid lamella. In the papillary dermis, there were prominent eosinophilic amorphous materials which were positive to Dylon staining. Treatment with oral etretinate resulted in a remission of the skin lesions in this case.

Solid-phase synthesis of protected alpha-amino phosphonic acid oligomers.

By establishing both a highly efficient phosphonamidate formation and a RuCp-catalyzed cleavage of an allyl linker, the solid-phase synthesis of Fmoc-(GlyP(OBn))(6)-OH/DIEA, a protected form of a new type of unnatural peptide alpha-amino phosphonic acid oligomer (APO), has been realized.

Catalytic removal of N-allyloxycarbonyl groups using the [CpRu(IV)(pi-C3H5)(2-quinolinecarboxylato)]PF6 complex. A new efficient deprotecting method in peptide synthesis.

A variety of amines including even sterically less demanding and highly nucleophilic secondary amines have been efficiently deprotected without decarboxylative N-allylation from the corresponding N-allyloxycarbonyl (N-AOC) compounds by using a catalytic amount of [CpRu(IV)(pi-C3H5)(2-quinolinecarboxylato)]PF6 in the presence of 1 molar amount of trifluoromethanesulfonic acid, the general utility of which has been demonstrated by the efficient synthesis of a collagen protein unit tripeptide, Pro-Pro-Gly.

CpRuIIPF6/quinaldic acid-catalyzed chemoselective allyl ether cleavage. A simple and practical method for hydroxyl deprotection.

A cationic CpRu(II) complex in combination with quinaldic acid shows high reactivity and chemoselectivity for the catalytic deprotection of hydroxyl groups protected as allyl ethers. The catalyst operates in alcoholic solvents without the need for any additional nucleophiles, satisfying the practical requirements of operational simplicity, safety, and environmental friendliness. The wide applicability of this deprotection strategy to a variety of multifunctional molecules, including peptides and nucleosides, may provide new opportunities in protective group chemistry. [structure: see text]