Synthesis of 2-Thio-Substituted 1,6-Diazabicyclo[3.2.1]octane Derivatives, Potent ß-Lactamase Inhibitors.

Approval of avibactam by the FDA has led to the recognition of 1,6-diazabicyclo[3.2.1]octane (DBO) derivatives as attractive compounds for ß-lactamase inhibition. We achieved a concise and collective synthesis of 2-thio-substituted DBO derivatives. The synthesis involves diastereoselective photo-induced Barton decarboxylative thiolation, which can be applied to large-scale synthesis. The DBO analogues exhibited strong inhibitory activities against serine ß-lactamases and acceptable solution stabilities for clinical development.

Synthesis of a 6-CF3-Substituted 2-Amino-dihydro-1,3-thiazine ß-Secretase Inhibitor by N, N-Diethylaminosulfur Trifluoride-Mediated Chemoselective Cyclization.

The synthesis of a 6-CF3-substituted 2-amino-dihydro-1,3-thiazine via N, N-diethylaminosulfur trifluoride (DAST)-mediated cyclization of N-hydroxypropyl thiourea 6 is described. This reaction gave 6-CF3-1,3-thiazine 7 with high chemical yield and chemoselectivity, suppressing the common byproduct of oxazine 8. This new protocol enabled access to 6-CF3-substituted 1,3-thiazine ß-secretase inhibitor 2.

Pyrrolinone derivatives as a new class of P2X3 receptor antagonists Part 2: Discovery of orally bioavailable compounds.

Some P2X3 receptor antagonists have been developed as new therapeutic drugs for pain. We discovered a novel chemotype of P2X3 receptor antagonists with a pyrrolinone skeleton. Because of SAR studies to improve bioavailability of lead compound 2, compound (R)-24 was identified, which showed an analgesic effect against neuropathic pain by oral administration. We constructed a human P2X3 homology model as a template for the zebrafish P2X4 receptor, which agreed with SAR studies of pyrrolinone derivatives.

Rational Design of Novel 1,3-Oxazine Based ß-Secretase (BACE1) Inhibitors: Incorporation of a Double Bond To Reduce P-gp Efflux Leading to Robust Aß Reduction in the Brain.

Accumulation of Aß peptides is a hallmark of Alzheimer's disease (AD) and is considered a causal factor in the pathogenesis of AD. ß-Secretase (BACE1) is a key enzyme responsible for producing Aß peptides, and thus agents that inhibit BACE1 should be beneficial for disease-modifying treatment of AD. Here we describe the discovery and optimization of novel oxazine-based BACE1 inhibitors by lowering amidine basicity with the incorporation of a double bond to improve brain penetration. Starting from a 1,3-dihydrooxazine lead 6 identified by a hit-to-lead SAR following HTS, we adopted a p Ka lowering strategy to reduce the P-gp efflux and the high hERG potential leading to the discovery of 15 that produced significant Aß reduction with long duration in pharmacodynamic models and exhibited wide safety margins in cardiovascular safety models. This compound improved the brain-to-plasma ratio relative to 6 by reducing P-gp recognition, which was demonstrated by a P-gp knockout mouse model.

Discovery of Potent and Centrally Active 6-Substituted 5-Fluoro-1,3-dihydro-oxazine ß-Secretase (BACE1) Inhibitors via Active Conformation Stabilization.

ß-Secretase (BACE1) has an essential role in the production of amyloid ß peptides that accumulate in patients with Alzheimer's disease (AD). Thus, inhibition of BACE1 is considered to be a disease-modifying approach for the treatment of AD. Our hit-to-lead efforts led to a cellular potent 1,3-dihydro-oxazine 6, which however inhibited hERG and showed high P-gp efflux. The close analogue of 5-fluoro-oxazine 8 reduced P-gp efflux; further introduction of electron withdrawing groups at the 6-position improved potency and also mitigated P-gp efflux and hERG inhibition. Changing to a pyrazine followed by optimization of substituents on both the oxazine and the pyrazine culminated in 24 with robust Aß reduction in vivo at low doses as well as reduced CYP2D6 inhibition. On the basis of the X-ray analysis and the QM calculation of given dihydro-oxazines, we reasoned that the substituents at the 6-position as well as the 5-fluorine on the oxazine would stabilize a bioactive conformation to increase potency.

The hypervariable domain of the mitochondrial control region in Atlantic spiny lobsters and its potential as a marker for investigating phylogeographic structuring.

Atlantic spiny lobsters support major fisheries in northeastern Brazilian waters and in the Caribbean Sea. To avoid reduction in diversity and elimination of distinct stocks, understanding their population dynamics, including structuring of populations and genetic diversity, is critical. We here explore the potential of using the hypervariable domain in the control region of the mitochondrial DNA as a genetic marker to characterize population subdivision in spiny lobsters, using Panulirus argus as the species model. The primers designed on the neighboring conserved genes have amplified the entire control region (approx. 780 bases) of P. argus and other closely related species. Average nucleotide and haplotype diversity within P. argus were found to be high, and population structuring was hypothesized. The data suggest a division of P. argus into genetically different phylogeographic groups. The hypervariable domain seems to be useful for determining genetic differentiation of geographically distinct stocks of P. argus and other Atlantic spiny lobsters.