Chemical Tagging of Bioactive Amides by Cooperative Catalysis: Applications in the Syntheses of Drug Conjugates.

We disclose a practical catalytic method for arming bioactive amide-based natural products and other small-molecule drugs with various functional handles for the synthesis of drug conjugates. We demonstrate that a set of readily available Sc-based Lewis acids and N-based Brønsted bases can function cooperatively to deprotonate amide N-H bonds in polyfunctional drug molecules. An aza-Michael reaction between the resulting amidate and α,ß-unsaturated compounds produces an array of drug analogues that are equipped with an alkyne, azide, maleimide, tetrazine, or diazirine moiety under redox and pH-neutral conditions. The utility of this chemical tagging strategy is showcased through the production of drug conjugates by the click reaction between the alkyne-tagged drug derivatives and an azide-containing green fluorescent protein, nanobody, or antibody.

Biphenyl Cyclobutenone Photoelectrocyclizations.

In this work, we demonstrate that readily available conjugated bis-aryl cyclobutenones undergo photoelectrocyclization reactions to give the corresponding dihydrophenanthrene cyclobutanones when exposed to 350 nm light, TFA, and TMSCl. We have also found that cyclobutenone electrocyclizations and cycloreversions are in equilibrium.

DBU-Catalyzed Desymmetrization of Cyclohexadienones: Access to Vicinal Diamine-Containing Heterocycles.

A DBU-catalyzed desymmetrization strategy between cyclohexadienones and isocyanates was discovered, affording a series of vicinal diamine-containing heterocycle derivatives in moderate to good yields and excellent diastereoselectivity under mild conditions. Furthermore, this reaction could be performed on a 10 g scale using 1.0 mol % of catalyst loading.