3-Aryl-3-arylmethoxyazetidines. A new class of high affinity ligands for monoamine transporters

Structure-Activity Relationship Studies of the Aryl Acetamide Triazolopyridazines against Cryptosporidium Reveals Remarkable Role of Fluorine

Our previous work identified compound 1 (SLU-2633) as a potent lead compound toward the identification of a novel treatment for cryptosporidiosis, caused by the parasite Cryptosporidium (EC50 = 0.17 μM). While this compound is potent and orally efficacious, the mechanism of action and biological target(s) of this series are currently unknown. In this study, we synthesized 70 compounds to develop phenotypic structure-activity relationships around the aryl "tail" group. In this process, we found that 2-substituted compounds are inactive, confirmed that electron withdrawing groups are preferred over electron donating groups, and that fluorine plays a remarkable role in the potency of these compounds. The most potent compound resulting from this work is SLU-10482 (52, EC50 = 0.07 μΜ), which was found to be orally efficacious with an ED90 < 5 mg/kg BID in a Cryptosporidium-infection mouse model, superior to SLU-2633.

"Magic Chloro": Profound Effects of the Chlorine Atom in Drug Discovery

Chlorine is one of the most common atoms present in small-molecule drugs beyond carbon, hydrogen, nitrogen, and oxygen. There are currently more than 250 FDA-approved chlorine-containing drugs, yet the beneficial effect of the chloro substituent has not yet been reviewed. The seemingly simple substitution of a hydrogen atom (R = H) with a chlorine atom (R = Cl) can result in remarkable improvements in potency of up to 100,000-fold and can lead to profound effects on pharmacokinetic parameters including clearance, half-life, and drug exposure in vivo. Following the literature terminology of the "magic methyl effect" in drugs, the term "magic chloro effect" has been coined herein. Although reports of 500-fold or 1000-fold potency improvements are often serendipitous discoveries that can be considered "magical" rather than planned, hypotheses made to explain the magic chloro effect can lead to lessons that accelerate the cycle of drug discovery.

Oxidative Deconstruction of Azetidinols to α-Amino Ketones

A silver-mediated synthesis of α-amino ketones via the oxidative deconstruction of azetidinols has been developed using a readily scalable protocol with isolated yields up to 80%. The azetidinols are easily synthesized in one step and can act as protecting groups for these pharmaceutically relevant synthons. Furthermore, mechanistic insights are presented and these data have revealed that the transformation is likely to proceed through the β-scission of an alkoxy radical, followed by oxidation and C-N cleavage of the resulting α-amido radical.

Synthesis of Simple 3,3-Diarylazetidines from N-Boc-3-arylazetidinols Using Friedel-Crafts Arylation Conditions

A synthesis of 3,3-diarylazetidines from N-Boc-3-aryl-3-azetidinols using Friedel-Crafts arylation conditions with AlCl₃ is described. A series of substituted diarylazetidines were readily prepared and isolated as the oxalate salts in high yield and high purity. The 3,3-diarylazetidine oxalates were then easily converted into N-alkyl and N-acyl analogues (RX, NaHCO₃/DMF/100 °C) in high overall yields.

Synthesis of 3,3-Diarylazetidines by Calcium(II)-Catalyzed Friedel-Crafts Reaction of Azetidinols with Unexpected Cbz Enhanced Reactivity

Azetidines are valuable motifs that readily access under explored chemical space for drug discovery. 3,3-Diarylazetidines are prepared in high yield from N-Cbz azetidinols in a calcium(II)-catalyzed Friedel-Crafts alkylation of (hetero)aromatics and phenols, including complex phenols such as β-estradiol. Electron poor phenols undergo O-alkylation. The product azetidines can be derivatized to drug-like compounds through the azetidine nitrogen and the aromatic groups. The N-Cbz group is crucial to reactivity by providing stabilization of an intermediate carbocation on the four-membered ring.