Design and four step synthesis of simple, readily accessible low-nanomolar divalent LecA ligands with selectivity over human galectin-1.

The Matteson homologation with vinyl nucleophiles was found to be a versatile tool for the synthesis of highly substituted and functionalized allyl boronic esters. High yields and stereoselectivities are obtained with sterically demanding alkyl boronic esters and/or Grignard reagents. With the application of such vinyl Matteson homologations, the polyketide fragment of lagunamide B is synthesized.

N-Methylated amino acids and peptides with an 8-aminoquinoline (AQ) directing group can be subjected to stereoselective Pd-catalyzed β-functionalizations. The best results are obtained with aryl iodides, but alkyl and alkenyl side chains can also be introduced. The AQ protecting group can easily be removed, providing the free carboxylic acid, which can be used directly in peptide couplings. This protocol was used successfully as a key step in the synthesis of the cyclopeptide alkaloids abyssenine A and mucronine E.

2-(Methylthio)aniline (MTA) directed C(sp3)–H functionalisations are efficient and straightforward protocols for the selective β-modification of N-methylated amino acids.