Macrocycles are of increasing interest as chemical probes and drugs for intractable targets like protein-protein interactions, but the determinants of their cell permeability and oral absorption are poorly understood. To enable rational design of cell-permeable macrocycles, we generated an extensive data set under consistent experimental conditions for more than 200 non-peptidic, de novo-designed macrocycles from the Broad Institute's diversity-oriented screening collection. This revealed how specific functional groups, substituents and molecular properties impact cell permeability. Analysis of energy-minimized structures for stereo- and regioisomeric sets provided fundamental insight into how dynamic, intramolecular interactions in the 3D conformations of macrocycles may be linked to physicochemical properties and permeability. Combined use of quantitative structure-permeability modeling and the procedure for conformational analysis now, for the first time, provides chemists with a rational approach to design cell-permeable non-peptidic macrocycles with potential for oral absorption.

Diazirines are widely used in photoaffinity labeling (PAL) to trap non-covalent interactions with biomolecules. However, design and interpretation of PAL experiments is challenging without a molecular understanding of the reactivity of diazirines with protein biomolecules.Here, we report a systematic evaluation of the labeling preferences of alkyl and aryl diazirines with individual amino acids, single proteins, and in the whole cell proteome. We find that aryl-fluorodiazirines react primarily through a carbene intermediate, while alkyl diazirines generate a reactive alkyl diazo intermediate on route to the carbene. The generation of a reactive diazo intermediate leads to preferential labeling of acidic amino acids in a pH-dependent manner. From a survey of 32 alkyl diazirine probes, we use this reactivity profile to rationalize why these probes preferentially enrich highly acidic proteins or those embedded in membranes and why probes with a net positive-charge tend to produce higher labeling yields. These results indicate that alkyl diazirines are an especially effective chemistry for surveying the membrane proteome, and will facilitate probe design and interpretation of biomolecular labeling experiments with diazirines.

In an effort to discover novel selective monoamine oxidase (MAO) B inhibitors with favorable physicochemical and pharmacokinetic profiles, 7-[(m-halogeno)benzyloxy]coumarins bearing properly selected polar substituents at position 4 were designed, synthesized, and evaluated as MAO inhibitors. Several compounds with MAO-B inhibitory activity in the nanomolar range and excellent MAO-B selectivity (selectivity index SI > 400) were identified. Structure-affinity relationships and docking simulations provided valuable insights into the enzyme-inhibitor binding interactions at position 4, which has been poorly explored. Furthermore, computational and experimental studies led to the identification and biopharmacological characterization of 7-[(3-chlorobenzyl)oxy]-4-[(methylamino)methyl]-2H-chromen-2-one methanesulfonate 22b (NW-1772) as an in vitro and in vivo potent and selective MAO-B inhibitor, with rapid blood-brain barrier penetration, short-acting and reversible inhibitory activity, slight inhibition of selected cytochrome P450s, and low in vitro toxicity. On the basis of this preliminary preclinical profile, inhibitor 22b might be viewed as a promising clinical candidate for the treatment of neurodegenerative diseases.