Synthesis and evaluation of novel dual BRD4/HDAC inhibitors.

Epigenetic regulation of gene expression via histone acetylation modulates many cellular processes, including apoptosis, the cell cycle, cell growth and differentiation, and inhibitors are promising drug candidates. We have previously developed inhibitors of BRD4, which recognizes acetylated lysine residue on histones and recruits transcription elongation factor to the transcription start site, while inhibitors of histone deacetylase (HDAC), which catalyzes the removal of acetyl groups on histones, are already in clinical use for cancer treatment. Based on the idea that polypharmacological agents with multiple targets would have a more robust action, we set out to develop dual BRD4/HDAC inhibitors. Here, we describe the design and synthesis of N6-[2-(7-hydroxyamino-7-oxoheptyloxy)benzoyl]adenine (5d) as a BRD4/HDAC dual inhibitor. This compound showed HL-60 cell growth-inhibitory and apoptosis-inducing activity, as well as all-trans retinoic acid (ATRA)-induced HL-60 cell differentiation-enhancing activity, and c-MYC production-inhibitory activity. Interestingly, it also showed growth-inhibitory activity towards BRD4 inhibitor-resistant cells.

Discovery and structure-activity relationship studies of N6-benzoyladenine derivatives as novel BRD4 inhibitors.

Bromodomain and extra-terminal domain (BET) proteins are epigenetic readers that bind to acetylated lysines in histones. Among them, BRD4 is a candidate target molecule of therapeutic agents for diverse diseases, including cancer and inflammatory disease. As a part of our continuing structural development studies of thalidomide to obtain a broad spectrum of biological modifiers based on the 'multi-template' approach, in this work we focused on BRD4-inhibitory activity, and discovered that N6-benzoyladenine derivatives exhibit this activity. Structure-activity relationship studies led to N6-(2,4,5-trimethoxybenzoyl)adenine (29), which exhibits potent BRD4 bromodomain1 inhibitory activity with an IC50 value of 0.427µM. N6-Benzoyladenine appears to be a new chemical scaffold for development of BRD4 inhibitors.

Supra-molecular architecture in a co-crystal of the N(7)-H tautomeric form of N (6)-benzoyl-adenine with adipic acid (1/0.5).

The asymmetric unit of the title co-crystal, C12H9N5O·0.5C6H10O4, consists of one mol-ecule of N (6)-benzoyl-adenine (BA) and one half-mol-ecule of adipic acid (AA), the other half being generated by inversion symmetry. The dihedral angle between the adenine and phenyl ring planes is 26.71 (7)°. The N (6)-benzoyl-adenine mol-ecule crystallizes in the N(7)-H tautomeric form with three non-protonated N atoms. This tautomeric form is stabilized by intra-molecular N-H⋯O hydrogen bonding between the carbonyl (C=O) group and the N(7)-H hydrogen atom on the Hoogsteen face of the purine ring, forming an S(7) ring motif. The two carboxyl groups of adipic acid inter-act with the Watson-Crick face of the BA mol-ecules through O-H⋯N and N-H⋯O hydrogen bonds, generating an R 2 (2)(8) ring motif. The latter units are linked by N-H⋯N hydrogen bonds, forming layers parallel to (10-5). A weak C-H⋯O hydrogen bond is also present, linking adipic acid mol-ecules in neighbouring layers, enclosing R (2) 2(10) ring motifs and forming a three-dimensional structure. C=O⋯π and C-H⋯π inter-actions are also present in the structure.

An easy microwave-assisted synthesis of C8-alkynyl adenine pyranonucleosides as novel cytotoxic antitumor agents.

We describe the synthesis of C8-alkynyl adenine pyranonucleosides 4, 5, and 8-phenylethynyl-adenine (II), via Sonogashira cross-coupling reaction under microwave irradiation. Compounds 4e and II were less cytostatic than 5-fluorouracil (almost an order of magnitude) against murine leukemia (L1210) and human cervix carcinoma (HeLa) cells, while the same compounds proved to be more active than 5-fluorouracil against human lymphocyte (CEM) cells.

Supramolecular hydrogen-bonding patterns in two cocrystals of the N(7)-H tautomeric form of N(6)-benzoyladenine: N(6)-benzoyladenine-3-hydroxypyridinium-2-carboxylate (1/1) and N(6)-benzoyladenine-DL-tartaric acid (1/1).

Two novel cocrystals of the N(7)-H tautomeric form of N(6)-benzoyladenine (BA), namely N(6)-benzoyladenine-3-hydroxypyridinium-2-carboxylate (3HPA) (1/1), C12H9N5O·C6H5NO3, (I), and N(6)-benzoyladenine-DL-tartaric acid (TA) (1/1), C12H9N5O·C4H6O6, (II), are reported. In both cocrystals, the N(6)-benzoyladenine molecule exists as the N(7)-H tautomer, and this tautomeric form is stabilized by intramolecular N-H···O hydrogen bonding between the benzoyl C=O group and the N(7)-H hydrogen on the Hoogsteen site of the purine ring, forming an S(7) motif. The dihedral angle between the adenine and phenyl planes is 0.94 (8)° in (I) and 9.77 (8)° in (II). In (I), the Watson-Crick face of BA (N6-H and N1; purine numbering) interacts with the carboxylate and phenol groups of 3HPA through N-H···O and O-H···N hydrogen bonds, generating a ring-motif heterosynthon [graph set R2(2)(6)]. However, in (II), the Hoogsteen face of BA (benzoyl O atom and N7; purine numbering) interacts with TA (hydroxy and carbonyl O atoms) through N-H···O and O-H···O hydrogen bonds, generating a different heterosynthon [graph set R2(2)(4)]. Both crystal structures are further stabilized by π-π stacking interactions.