SbCl5-wet acetonitrile: a new system for chemoselective O-desilylation

A new efficient method for deprotection of TBDMS derivatives of phenols, primary alcohols, carboxylic acids and secondary amines, consisting of SbCl₅ and MeCN with 0.1% water (w/v), is reported. It effects inter alia desilylation of a CH₂OTBDMS group in the presence of a ketal function.     

Construction of β-Phenylalanine Derivatives through Pd-Catalyzed,C(sp2)−H (ortho) Functionalization

This paper describes the Pd(II)-catalyzed, picolinamide-directing-group-aided C(sp²)−H (ortho) functionalization of racemic and enantiopure β-phenylalanines and 3-amino-3-phenylpropanols (1,3-amino alcohols). The C(sp²)−H (ortho) functionalizations including arylation, bromination, iodination, and alkoxylation were attempted. The C(sp²)−H (ortho) arylation reactions gave biaryl or terphenyl-type β-phenylalanine scaffolds, halogenation and methoxylation reactions gave ortho C−H halogenated or methoxylated β-phenylalanines. Additionally, the C−H arylation of an ortho-methyl substituted β-phenylalanine containing both C(sp²)−H and remote C(sp³)−H bonds was investigated. β-Phenylalanine is an arylated β-amino acid motif present in various natural products, bioactive molecules, and β-peptides and it is a precursor to medicinally active compounds. Accordingly, this work contributes to the expansion of the library of unnatural β-phenylalanine (β-amino acid) derivatives through site-selective C−H functionalization.     

Dissociation of gas-phase dimeric complexes of lactic acid and transition-metal ions formed under electrospray ionization conditions; the role of reduction of the metal ion

Dimeric complex ions of the type [M(A-H)A]+, where M=metal ion (Co, Ni, Cu, and Zn) and A=ligand (lactic acid, methyl lactate or ethyl lactate), were generated in the gas phase under electrospray ionization conditions. The collision-induced dissociation spectra of [M(A-H)A]+ ions were recorded to study the behaviour of ligand and metal ions in decomposition of these dimeric complex ions. Based on the fragmentation pathways observed for complex ions of lactic acid, it is found that both the carboxylic and hydroxyl groups of lactic acid are involved in the complex formation following displacement of a proton by the metal ion. The dimeric complex ions of Co, Ni, and Zn dissociated to yield similar types of ions, whereas that of Cu behaved differently. The dissociations of Co-, Ni-, and Zn-bound dimeric complexes involved losses of neutral molecules while keeping the oxidation state of the metal ion unchanged. However, elimination of radicals is found in the dissociation of dimeric complex ions of Cu, and the oxidation state of copper is reduced from Cu(II) to Cu(I) in the resulting fragment ions. The deprotonated ligand is involved in the fragmentation pathway of Cu complexes, whereas it is intact in other complexes. The oxidation state of the metal ion, nature of the ligand, and site of attachment to the metal ion are found to control the dissociation of these dimeric complex ions.     

Stereoselective Synthesis of HIV-1 Protease Inhibitor, DMP 323

DMP 323, a potent HIV-1 protease inhibitor, has been synthesized by an efficient stereoselective process, amenable to large scale preparations. The core C(2) symmetric diol was synthesized by a stereoselective pinacol coupling of CBZ protected D-phenylalanine. Judicious selection of protecting groups allowed cyclic urea formation under mild conditions, enhanced the ease of bis-alkylation, and led to intermediates which were easily purified without chromatography. Additionally, a one-pot, high yield process was developed to prepare the alkylating agent, 4-[(triphenylmethoxy)methyl]benzyl chloride from 1,4-benzenedimethanol.     

A formal synthesis of (±)-physostigmine via 3,3-rearrangement of a bis-enamine

A new flexible approach to hexahydropyrrolo[2,3-b]indole system via the [3,3]-sigmatropic rearrangement of 1-(2′-methoxycarbonyl-N-methylvinylamino)skatole, culminating in the synthesis of (±)-desoxyeseroline, is described.     

In vitro antimicrobial-activity studies on the mixed ligand complexes of Hg(II) with 8-hydroxyquinoline and salicylic acids

A series of mixed ligand complexes of Hg(II) with the general formula Hg (OX) (SA) (where OX: 8-hydroxyquinoline, SA: salicylic, 5-chloro-, 3,5-dibromo, 3,5-diiodo, 3,5-dinitro, acetyl thiosalicylic acids) are isolated in pure state and characterised by elemental analysis and infrared data. The low molar conductance of the complexes in dimethylformamide indicates non-electrolyte nature. The antimicrobial activity of these complexes against various bacteria and fungi is studied which indicates that in several cases, the mixed ligand complexes possess fairly highly antimicrobial activity than the binary mercury-oxinate. The lipophilic tendency of these complexes and its influence on the antimicrobial activity is critically examined. A probable mechanism for the toxic action of these complexes against various organisms is discussed.     

Mass spectral studies of a series of N,N-dialkyl aminoethyl-2-chlorides and trimethyl silyl ethers of N,N-dialkyl aminoethane-2-ols under electron impact conditions

The electron impact (EI) mass spectra of a series of N,N-dialkyl-aminoethyl-2-chlorides, N(R(1))(R(2))-CH(2)-CH(2)Cl and trimethylsilyl ethers of N,N-dialkyl aminoethane-2-ols, N(R(1))(R(2))-CH(2)-CH(2)-O-Si(CH(3))(3), where R(1) and R(2) = methyl, ethyl, propyl and isopropyl, which are precursors of VX type of compounds, are studied. All the compounds (1-20) show abundant molecular ions, in addition to a weak [M - H](+) ion, except the N,N-diisopropyl group containing compounds (8 and 18). A general EI fragmentation pattern for the above two series of compounds is discussed. The observed fragment ions are due to simple homolytic cleavages, and they are distinct to allow the identification of the compounds unequivocally including those of isomeric compounds. The primary fragmentation of compounds 1-20 is beta-cleavage, i.e. homolytic cleavage of C-C bond, which is linked to the nitrogen atom. Three types of beta-cleavages are possible for these compounds, in which the abundance of beta-cleavage product ions is found to depend on the size and structure of the alkyl group attached to nitrogen. The alpha-cleavage fragment ions are found only for N,N-dialkyl aminoethyl-2-chlorides but are absent in the corresponding trimethylsilyl ethers of N,N-dialkyl aminoethane-2-ols. The retention indices are calculated for all the studied compounds (1-20) and are in the ranges of 750.38-1079.24 for 1-10 and 905.23-1190.25 for 11-20.