Managing emerging mutagenicity risks: Late stage mutagenic impurity control within the atovaquone second generation synthesis.

The mutagenic-impurity control strategy for a second generation manufacturing route to the non-mutagenic antipneumocystic agent atovaquone (2-((1R,4R)-4-(4-chlorophenyl)cyclohexyl)-3-hydroxynaphthalene-1,4-dione) 1 is described. Preliminary assessment highlighted multiple materials of concern which were largely discharged either through returning a negative bacterial mutagenicity assay or through confidence that the impurity would be purged during the downstream processing from when it was first introduced. Additional genotoxicity testing highlighted two materials of concern where initial assessment suggested that testing for these impurities at trace levels within the drug substance would be required. Following a thorough review of process purging detail, spiking and purging experimentation, and an understanding of the process parameters to which they were exposed an ICH M7 Option 4 approach could be justified for their control. The development of two 1H NMR spectroscopy methods for measurement of these impurities is also described as well as a proposed summary table for describing the underlying rationale for ICH M7 control rationales to regulators. This manuscript demonstrates that process purging of potential mutagenic impurities can be realised even when they are introduced in the later stages of a process and highlights the importance of scientific understanding rather than relying on a stage-counting approach.

The generation and trapping of enantiopure bromonium ions.

Enantiopure bromonium ions may be generated from enantiopure bromohydrins and derivatives, they can be trapped with an in situ nucleophile to give enantiomerically pure products.

Ortho-substituted iodobenzenes as novel organocatalysts for bromination of alkenes.

Suitably ortho-substituted iodobenzenes act as organocatalysts for the transfer of electrophilic bromine from N-bromosuccinimide to alkenes via the intermediacy of bromoiodinanes.

Bromoiodinanes with an I(III)-Br bond: preparation, X-ray crystallography and reactivity as electrophilic brominating agents.

Bromoiodinanes--conveniently and directly prepared from iodobenzenecarbinols and N-bromosuccinimide, and characterised for the first time crystallographically--act as electrophilic bromine donors.

Discovery of 6-Amino-2-{[(1S)-1-methylbutyl]oxy}-9-[5-(1-piperidinyl)pentyl]-7,9-dihydro-8H-purin-8-one (GSK2245035), a Highly Potent and Selective Intranasal Toll-Like Receptor 7 Agonist for the Treatment of Asthma.

Induction of IFNα in the upper airways via activation of TLR7 represents a novel immunomodulatory approach to the treatment of allergic asthma. Exploration of 8-oxoadenine derivatives bearing saturated oxygen or nitrogen heterocycles in the N-9 substituent has revealed a remarkable selective enhancement in IFNα inducing potency in the nitrogen series. Further potency enhancement was achieved with the novel (S)-pentyloxy substitution at C-2 leading to the selection of GSK2245035 (32) as an intranasal development candidate. In human cell cultures, compound 32 resulted in suppression of Th2 cytokine responses to allergens, while in vivo intranasal administration at very low doses led to local upregulation of TLR7-mediated cytokines (IP-10). Target engagement was confirmed in humans following single intranasal doses of 32 of ≥20 ng, and reproducible pharmacological response was demonstrated following repeat intranasal dosing at weekly intervals.

Absolute stereochemistry assignment of N-phosphorylimine-derived aza-Diels-Alder adducts with TDDFT CD calculations.

N-phosphorylimines undergo Lewis acid-catalyzed Diels-Alder reactions with Danishefsky's diene. Application of the chiral catalyst zinc(II)-(S)-BINOL results in good-to-low asymmetric induction but poor chemical conversion. However, the absolute stereochemistry of novel aza-Diels-Alder cycloadducts, such as diethyl 4-oxo-2-phenyl-3,4-dihydropyridin-1(2H)-ylphosphonate, can be determined using circular dichroism (CD). Comparison between experimental and TDDFT-calculated CD spectrum shows that use of the (S)-catalyst results in predominant formation of the (6R) cycloadducts.

Mechanistic studies on the formal aza-Diels-Alder reactions of N-aryl imines: evidence for the non-concertedness under Lewis-acid catalysed conditions.

The reaction of a para-methoxyaniline, ethyl glyoxalate-derived imine with a series of dienes has resulted in products, which initially suggest the operation of different modes of aza-Diels-Alder reaction. However, a more likely explanation is that a common reaction mechanism is operating, involving a step-wise Lewis-acid catalysed process, which only appears to behave similarly to alternative concerted cycloaddition reactions.

Enantiopure bicyclic piperidinones: stereoselectivity in lactam enolate alkylations.

The synthesis and alkylation of [4.3.0]-bicyclic lactams, derived from 6-oxopipecolic acid, have been investigated. Alkylation can proceed with predominantly exo-diastereoselectivity, but the efficiency of this process depends on the substitution at the hemiaminal ether system. These products can be readily deprotected to give substituted hydroxymethyl lactams in good yield.