Class IIa histone deacetylases repress transcription of target genes. However, their mechanism of action is poorly understood because they exhibit very low levels of deacetylase activity. The class IIa HDACs are associated with the SMRT/NCoR repression complexes and this may, at least in part, account for their repressive activity. However, the molecular mechanism of recruitment to co-repressor proteins has yet to be established. Here we show that a repeated peptide motif present in both SMRT and NCoR is sufficient to mediate specific interaction, with micromolar affinity, with all the class IIa HDACs (HDACs 4, 5, 7, and 9). Mutations in the consensus motif abrogate binding. Mutational analysis of HDAC4 suggests that the peptide interacts in the vicinity of the active site of the enzyme and requires the “closed” conformation of the zinc-binding loop on the surface of the enzyme. Together these findings represent the first insights into the molecular mechanism of recruitment of class IIa HDACs to the SMRT/NCoR repression complexes.

A highly diastereoselective synthesis of (2S,3S)-β-hydroxy-α-amino acids has been developed from enantiopure α-hydroxy acids using a MOM-ether-directed, palladium(II)-catalysed, aza-Claisen rearrangement of allylic acetimidates to effect the key step. This highly stereoselective process gave allylic amides in diastereomeric ratios of up to 14 : 1. Problems associated with the isolation of 1,3-products (anti-Claisen) from sterically demanding substrates via an insitu palladium(0)-catalysed rearrangement process were overcome by the addition of a re-oxidant, p-benzoquinone, leading to cleaner reactions and improved yields of the 3,3-products (Claisen). The target β-hydroxy-α-amino acids are an important class of natural products that are also components of more complex organic compounds with significant biological properties.

The protein kinase PfCLK3 plays a critical role in the regulation of malarial parasite RNA splicing and is essential for the survival of blood stage Plasmodium falciparum. We recently validated PfCLK3 as a drug target in malaria that offers prophylactic, transmission blocking and curative potential. Herein we describe the synthesis of our initial hit TCMDC-135051 (1) and efforts to establish a structure−activity relationship (SAR) with a 7-azaindole-based series. A total of 14 analogues were assessed in a TR-FRET assay against the full-length recombinant protein kinase PfCLK3 and 11 analogues were further assessed in asexual 3D7 (chloroquine sensitive) strains of P. falciparum parasites. SAR relating to rings A and B was established. These data together with analysis of activity against parasites collected from patients in the field suggest that TCMDC-135051 (1) is a promising lead compound for the development of new antimalarials with a novel mechanism of action targeting PfCLK3.