A high-throughput screen of the NIH molecular libraries sample collection and subsequent optimization of a lead dipeptide-like series of severe acute respiratory syndrome (SARS) main protease (3CLpro) inhibitors led to the identification of probe compound ML188 (16-(R), (R)-N-(4-(tert-butyl)phenyl)-N-(2-(tert-butylamino)-2-oxo-1-(pyridin-3-yl)ethyl)furan-2-carboxamide, Pubchem CID: 46897844). Unlike the majority of reported coronavirus 3CLpro inhibitors that act via covalent modification of the enzyme, 16-(R) is a non-covalent SARS-CoV 3CLpro inhibitor with moderate MW and good enzyme and antiviral inhibitory activity. A multi-component Ugi reaction was utilized to rapidly explore structure activity relationships within S1′, S1, and S2 enzyme binding pockets. The X-ray structure of SARS-CoV 3CLpro bound with 16-(R) was instrumental in guiding subsequent rounds of chemistry optimization. 16-(R) provides an excellent starting point for the further design and refinement of 3CLpro inhibitors that act by a non-covalent mechanism of action.

Herein we report the discovery and SAR of a novel series of SARS-CoV 3CLpro inhibitors identified through the NIH Molecular Libraries Probe Production Centers Network (MLPCN). In addition to ML188, ML300 represents the second probe declared for 3CLpro from this collaborative effort. The X-ray structure of SARS-CoV 3CLpro bound with a ML300 analog highlights a unique induced-fit reorganization of the S2-S4 binding pockets leading to the first sub-micromolar non-covalent 3CLpro inhibitors retaining a single amide bond.

(S)-1,1'-Binaphth-2-ol (BINOL) in combination with ZnEt(2), Ti(O(i)Pr)(4), and biscyclohexylamine was found to catalyze the highly enantioselective (83-95% ee) addition of various 1,3-diynes to aldehydes of diverse structures. This method provides a convenient pathway to generate a number of optically active dienediynes as the acyclic precursors to polycyclic compounds. The chiral dienediynes undergo highly chemoselective Pauson-Khand (PK) cycloaddition in benzaldehyde by using [Rh(cod)Cl](2) as the catalyst in the presence of rac-BINAP. High diastereoselectivity (up to >20:1) has also been achieved with the chiral dienediyne substrates containing a bulky substituent adjacent to the chiral center. In the presence of the Grubbs II catalyst, ring-closing enyne metathesis of the PK cycloaddition products led to the formation of the desired 5,5,7- and 5,5,8-fused tricyclic compounds. Further highly diastereoselective Diels-Alder reaction of a 5,5,7-tricyclic compound with maleic anhydride produced a 5,5,7,6-polycyclic product. The asymmetric synthesis of polycyclic compounds from optically active dienediynes has established a novel and efficient synthetic route to the structural framework of many biologically significant molecules.

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ABSTRACT:The M 1 muscarinic acetylcholine receptor is thought to play an important role in memory and cognition, making it a potential target for the treatment of Alzheimer's disease (AD) and schizophrenia. Moreover, M 1 interacts with BACE1 and regulates its proteosomal degradation, suggesting selective M 1 activation could afford both palliative cognitive benefit as well as disease modification in AD. A key challenge in targeting the muscarinic acetylcholine receptors is achieving mAChR subtype selectivity. Our lab has previously reported the M 1 selective positive allosteric modulator ML169. Herein we describe our efforts to further optimize this lead compound by preparing analogue libraries and probing novel scaffolds. We were able to identify several analogues that possessed submicromolar potency, with our best example displaying an EC 50 of 310 nM. The new compounds maintained complete selectivity for the M 1 receptor over the other subtypes (M 2 −M 5 ), displayed improved DMPK profiles, and potentiated the carbachol (CCh)-induced excitation in striatal MSNs. Selected analogues were able to potentiate CCh-mediated nonamyloidogenic APPsα release, further strengthening the concept that M 1 PAMs may afford a disease-modifying role in the treatment of AD. KEYWORDS: Muscarinic, acetylcholine, positive allosteric modulator (PAM), ML169, Alzheimer's disease (AD), medium spiny neurons (MSNs), MLPCN T he muscarinic acetylcholine receptors (mAChRs) are members of the family A G-protein-coupled receptors (GPCRs) and comprise five subtypes (M 1 −M 5 ) that mediate a broad range of actions of the neurotransmitter acetylcholine (ACh, 1) in the central nervous system and other tissues (Figure 1) and play key roles in memory and attention mechanisms, motor control, nociception, regulation of sleepwake cycles, cardiovascular function, renal function, and GI function. 1 mAChR subtypes M 1 , M 3 , and M 5 are coupled to G q and stimulate phospholipase C and intracellular Ca 2+ release, while M 2 and M 4 are coupled to G i and block adenylyl cyclase. 2 Data from brain expression, cellular localization, and knockout mice have implicated that M 1 plays a vital role in both memory and cognition, 3 and numerous studies have shown efficacy in preclinical cognition models with selective M 1 activators. 4−7 Recently, studies have conclusively shown that M 1 interacts with BACE1 to regulate its protesomal degradation and that M 1 activation activates α-secretase, which leads to an increase in sAPPα thereby preventing the formation of Aβ via MAPK-and PKC-dependent pathways. 8 In addition, M 1 activation decreases τ phosphorylation; therefore, M 1 activation affects the major pathological hallmarks of AD. 8,9 Beyond the cholinergic and NMDA hypofunction hypotheses of schizophrenia where M 1 could play a critical therapeutic role, 10 BACE1 has also been linked to schizophrenia, via neuregulin 1; thus, the ability of M 1 activation to regulate BACE1 suggests that pharmacological agents that can selectivity activate M 1 represent a nove...

A family of optically active H(8)BINOL-AM compounds containing 3,3'-bis-tertiary amine substituents are synthesized by using a one-step reaction of H(8)BINOL with amino methanols that were in situ generated from various cyclic or acyclic secondary amines and paraformaldehyde. The H(8)BINOL-AM compounds are used to catalyze the reaction of functional arylzincs, in situ prepared from the reaction of aryliodides with ZnEt(2), with aldehydes to produce chiral diaryl carbinols and a few arylalkyl carbinols. Through this study, highly enantioselective catalysts were identified. It was found that the H(8)BINOL-AM compounds with sterically less congested cyclic or acyclic amino methyl substituents were more enantioselective than those with more bulky substituents. The pyrrolidinyl derivative (S)-12 in most cases showed greater enantioselectivity than other H(8)BINOL-AM compounds, especially for the challenging ortho-substituted aromatic aldehydes. A H(8)BINOL-AM with 3,3'-bis-sec-amine substituents, prepared by a multistep method, was also used to catalyze the arylzinc addition to aldehydes, but it showed enantioselectivity lower than that of the compounds with tertiary amine groups. It was found for the first time that an aryl bromide, 2-bromothiophene, could be used to prepare an arylzinc reagent by reaction with ZnEt(2). The addition of this heteroarylzinc reagent to an aldehyde in the presence of (S)-12 proceeded with good enantioselectivity.

Positive allosteric modulators (PAMs) of metabotropic glutamate receptor 5 (mGlu5) represent a promising therapeutic strategy for the treatment of schizophrenia. Both allosteric agonism and high glutamate fold-shift have been implicated in the neurotoxic profile of some mGlu5 PAMs; however, these hypotheses remain to be adequately addressed. To develop tool compounds to probe these hypotheses, the structure-activity relationship of allosteric agonism was examined within an acetylenic series of mGlu5 PAMs exhibiting allosteric agonism in addition to positive allosteric modulation (ago-PAMs). PAM 38t, a low glutamate fold-shift allosteric ligand (maximum fold-shift ~3.0), was selected as a potent PAM with no agonism in the in vitro system used for compound characterization and in two native electrophysiological systems using rat hippocampal slices. PAM 38t (ML254) will be useful to probe the relative contribution of cooperativity and allosteric agonism to the adverse effect liability and neurotoxicity associated with this class of mGlu5 PAMs.

A series of optically active BINOL, H(4)BINOL, and H(8)BINOL derivatives were prepared. These compounds in combination with ZnEt(2) and Ti(O(i)Pr)(4) were used to catalyze the asymmetric reaction of alkynes with aldehydes to generate chiral propargylic alcohols at room temperature. Through this comparative study, a 3,3'-bisanisyl-substituted H(8)BINOL (S)-7 was found to be a generally enantioselective catalyst for the reaction of structurally diverse terminal alkynes with a variety of aldehydes. It catalyzed the reactions of alkyl propiolates with 88-99% ee; the reactions of phenylacetylene with 81-87% ee; the reactions of 4-phenyl-1-butyne, an alkyl alkyne, with 77-89% ee; and the reactions of trimethylsilylacetylene with 92-97% ee. The optically active propargylic alcohols generated from this catalytic asymmetric alkyne addition were observed to undergo efficient ring-closing-metathesis (RCM) reaction in the presence of the Grubbs II catalyst to produce chiral cycloalkenes. It was further found that some of the chiral propargylic alcohols underwent a highly chemoselective tandem RCM hydrogenation reaction with retention of the enantiomeric purity.