An efficient multigram synthesis of the potent histamine H3 antagonist GT-2331 and the reassessment of the absolute configuration

GT-2331 is a potent histamine H(3) antagonist which has entered clinical trials. Efficient multigram syntheses of this compound and its enantiomer are described. The literature reports that GT-2331 is the dextrorotatory (+), more potent, enantiomer of 4-[2-(5,5-dimethylhex-1-ynyl)cyclopropyl]-1H-imidazole with the absolute configuration of (1R,2R)-1. However, we found that the dextrorotatory, more potent, enantiomer of 4-[2-(5,5-dimethylhex-1-ynyl)cyclopropyl]-1H-imidazole has the (1S,2S) absolute configuration. We suggest a reconsideration of the absolute configuration of GT-2331.     

Mapping tertiary interactions in protein folding reactions: a novel mass spectrometry- and chemical synthesis-based approach

A novel mass spectrometry- and chemical synthesis-based approach for studying protein folding reactions is described, and its initial application to study the folding/unfolding reaction of a homo-hexameric enzyme 4-oxalocrotonate (4OT) is reported. This new approach involves the application of total chemical synthesis to prepare protein analogues that contain a photoreactive amino acid site-specifically incorporated into their primary amino acid sequence. To this end, a photoreactive amino acid-containing analogue of 4OT in which Pro-1 was replaced with p-benzoyl-l-phenylalanine (Bpa) was prepared. This analogue can be used to map structurally specific protein-protein interactions in 4OT's native folded state. These photocrosslinking studies and peptide mapping results with (PlBpa)4OT indicate that this construct is potentially useful for probing the structural properties of equilibrium and kinetic intermediates in 4OT's folding reaction.     

The formation of neutral CCCO2H and HCCCO2 molecules from anionic precursors in the gas phase: a joint experimental and theoretical study

Calculations at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31G(d) level of theory indicate that the anions -CCCO2H and HCCCO2(-) are stable species in their singlet states. Upon collision-induced, vertical one-electron oxidation under neutralisation-reionisation (-NR+) conditions, they produce the neutral molecules CCCO2H and HCCCO2, respectively. Some of the CCCO2H neutrals should be stable for the duration of the neutralisation-reionisation experiment (10(-6) s), while others will dissociate to CCCO and OH (requires 125 kJ mol(-1)). In contrast, neutral HCCCO2 is expected to be much less stable, and dissociate to HCC and CO2 (37 kJ mol(-1)). Neither CCCO2H nor HCCCO2 is expected to interconvert, or to rearrange to other isomers. The anions -CCCO2H and HCCCO2(-) have been formed in the ion source of the mass spectrometer by the reactions between (CH3)3Si-C[triple bond]C-CO2H and F- and HC[triple bond]C-CO2Si(CH3)3 and F-, respectively. The -NR+ spectrum of -CCCO2H shows a recovery signal and also indicates that the lowest energy dissociation pathway of neutral CCCO2H corresponds to the loss of OH. The -NR+ spectrum of HCCCO2 displays little or no recovery signal, and the spectrum is dominated by the [CO2]+ ion. The experimental observations are in agreement with the predictions of the extensive theoretical studies.     

Parallel synthesis and in vitro activity of novel anthranilic hydroxamate-based inhibitors of the prostaglandin H2 synthase peroxidase activity

Currently available non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin are directed at the cyclooxygenase (COX) site, but not the peroxidase (POX) activity of prostaglandin H2 synthase (PGHS). They are thus unable to inhibit the free-radical induced tissue injury associated with PGHS peroxidase activity, which can occur independently of the COX site. A lead compound, anthranilic hydroxamic acid (AHA) was found to have significant PGHS-POX inhibitory activity (IC50= 72 microM). To define the critical parameters for PGHS-POX inhibition, we investigated 29 AHA derivatives, synthesised from their acid precursors, using solid phase synthesis. In vitro analysis demonstrated a ten-fold improvement in inhibition with 3,5-diiodoanthranilic hydroxamic acid (IC50= 7 microM).     

One-electron oxidation of [CCOCC]-* in the gas phase forms stable and decomposing forms of CCCCO

The radical anion [CCOCC]-* may be made in the source of a VG ZAB 2HF mass spectrometer by the reaction between F-(from SF6) and (CH3)3SiC[triple bond]COC[triple bond]CSi(CH3)3. Vertical (Franck-Condon) one-electron oxidation of [CCOCC]-* in the first collision cell produces both singlet and triplet CCOCC. A combination of experiment and molecular modelling (at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-31G* level of theory) gives data which are consistent with the CCOCC neutrals rearranging over small barriers to form singlet and triplet CCCCO in exothermic reactions. Both singlet and triplet CCCCO formed in this way have excess energy. Singlet CCCCO has sufficient excess energy to effect decomposition exclusively to CCC and CO. In contrast, some of the triplet CCCCO neutrals are stable, while others decompose to CCC and CO.     

Inelastic neutron scattering study of commensurate-incommensurate phase transition in thiourea

This paper presents a study of the nature of the incommensurate lattice instability in deuterated thiourea by inelastic neutron scattering. It shows clearly a “soft mode” which condenses at the phase transition in a satellite reflexion. A study of related dispersion curves along the [O ξ O] direction shows an unusual spectral shape in a large temperature range above T_c.     

Momentum transfer in crystal lattices with vibrating atoms

A momentum transfer equation previously used to describe non-elastic deformation in crystalline solids represented by point masses at fixed lattice positions is extended to take into account the existence of intrinsic (e.g. thermal) small amplitude vibrations of the masses about their mean positions in a lattice. Use of the time-dependent Schroedinger equation to describe momentum transfer and deformation is also discussed in terms of this vibrating point-mass lattice model. The result is that a modified and identical differential equation for momentum transfer is obtained from each approach; some solutions to this equation are presented. The previous particle momentum wave frequency dependence on wave vector and resulting applications to non-elastic deformation are unchanged, but these particle momentum waves can now be considered as modulating the usual high-frequency waves associated with the elastic modes of a crystalline solid.