An organocatalyst-mediated protein aldol ligation (OPAL) affords C–C linked bioconjugates at neutral pH.

The pyrrolysine tRNA synthetase-tRNA pair is probably one of the most promiscuous tRNA-synthetase pairs found in nature, capable of genetically encoding a plethora of noncanonical amino acids through stop codon reassignment. Proteins containing reactive handles, post-translational modification mimics or both can be produced in practical quantities, allowing inter alia the probing of biological pathways, generating antibody-drug conjugates and enhancing protein function. This Minireview summarises the development of pyrrolysine amber stop-codon suppression, presents some of the considerations required to utilise this technique to its greatest potential, and showcases the creative ways in which this technique has led to a better understanding of biological systems.

Protein bioconjugation frequently makes use of aldehydes as reactive handles, with methods for their installation being highly valued. Here a new, powerful strategy to unmask a reactive protein aldehyde is presented. A genetically encoded caged glyoxyl aldehyde, situated in solvent-accessible locations, can be rapidly decaged through treatment with just one equivalent of allylpalladium(ii) chloride dimer at physiological pH. The protein aldehyde can undergo subsequent oxime ligation for site-selective protein modification. Quick yet mild conditions, orthogonality and powerful exposed reactivity make this strategy of great potential in protein modification.

The utility of sulfoxides in a diverse range of transformations in the field of carbohydrate chemistry has seen rapid growth since the first introduction of a sulfoxide as a glycosyl donor in 1989. Sulfoxides have since developed into more than just anomeric leaving groups, and today have multiple roles in glycosylation reactions. These include as activators for thioglycosides, hemiacetals, and glycals, and as precursors to glycosyl triflates, which are essential for stereoselective β‐mannoside synthesis, and bicyclic sulfonium ions that facilitate the stereoselective synthesis of α‐glycosides. In this review we highlight the mechanistic investigations undertaken in this area, often outlining strategies employed to differentiate between multiple proposed reaction pathways, and how the conclusions of these investigations have and continue to inform upon the development of more efficient transformations in sulfoxide‐based carbohydrate synthesis.