Initial development of a cytotoxic amino-<em>seco</em>-CBI warhead for delivery by prodrug systems

Cyclopropabenzaindoles (CBIs) are exquisitely potent cytotoxins which bind and alkylate in the minor groove of DNA. They are not selective for cancer cells, so prodrugs are required. CBIs can be formed at physiological pH by Winstein cyclisation of 1-chloromethyl-3-substituted-5-hydroxy-2,3-dihydrobenzo[e]indoles (5-OH-seco-CBIs). Corresponding 5-NH2-seco-CBIs should also undergo Winstein cyclisation similarly. A key triply orthogonally protected intermediate on the route to 5-NH2-seco-CBIs has been synthesised, via selective monotrifluoroacetylation of naphthalene-1,3-diamine, Boc protection, electrophilic iodination, selective allylation at the trifluoroacetamide and 5-exo radical ring-closure with TEMPO. This intermediate has potential for introduction of peptide prodrug masking units (deactivating the Winstein cyclisation and cytotoxicity), addition of diverse indole-amide side-chains (enhancing non-covalent binding prior to alkylation) and use of different leaving groups (replacing the usual chlorine, allowing tuning of the rate of Winstein cyclisation). This key intermediate was elaborated into a simple model 5-NH2-seco-CBI with a dimethylaminoethoxyindole side-chain. Conversion to a bio-reactive entity and the bioactivity of this system were confirmed through DNA-melting studies (ΔTm=13°C) and cytotoxicity against LNCaP human prostate cancer cells (IC50=18nM).</p

Exploration of the nicotinamide-binding site of the tankyrases, identifying 3-arylisoquinolin-1-ones as potent and selective inhibitors <em>in vitro</em>

Tankyrases-1 and -2 (TNKS-1 and TNKS-2) have three cellular roles which make them important targets in cancer. Using NAD(+) as a substrate, they poly(ADP-ribosyl)ate TRF1 (regulating lengths of telomeres), NuMA (facilitating mitosis) and axin (in wnt/β-catenin signalling). Using molecular modelling and the structure of the weak inhibitor 5-aminoiso quinolin-1-one, 3-aryl-5-substituted-isoquinolin-1-ones were designed as inhibitors to explore the structure-activity relationships (SARs) for binding and to define the shape of a hydrophobic cavity in the active site. 5-Amino-3-arylisoquinolinones were synthesised by Suzuki-Miyaura coupling of arylboronic acids to 3-bromo-1-methoxy-5-nitro-isoquinoline, reduction and O-demethylation. 3-Aryl-5-methylisoquinolin-1-ones, 3-aryl-5-fluoroisoquinolin-1-ones and 3-aryl-5-methoxyisoquinolin-1-ones were accessed by deprotonation of 3-substituted-N,N,2-trimethylbenzamides and quench with an appropriate benzonitrile. SAR around the isoquinolinone core showed that aryl was required at the 3-position, optimally with a para-substituent. Small meta-substituents were tolerated but groups in the ortho-positions reduced or abolished activity. This was not due to lack of coplanarity of the rings, as shown by the potency of 4,5-dimethyl-3-phenylisoquinolin-1-one. Methyl and methoxy were optimal at the 5-position. SAR was rationalised by modelling and by crystal structures of examples with TNKS-2. The 3-aryl unit was located in a large hydrophobic cavity and the para-substituents projected into a tunnel leading to the exterior. Potency against TNKS-1 paralleled potency against TNKS-2. Most inhibitors were highly selective for TNKSs over PARP-1 and PARP-2. A range of highly potent and selective inhibitors is now available for cellular studies.</p

Amide-controlled, one-pot synthesis of tri-substituted purines generates structural diversity and analogues with trypanocidal activity

Anovel one-pot synthesis of tri-substituted purines and the discovery of purine analogues with trypanocidal activity are reported. The reaction is initiated by a metal-free oxidative coupling of primary alkoxides and diaminopyrimidines with Schiff base formation and subsequent annulation in the presence of large N,N-dimethylamides (e.g.N,N-dimethylpropanamide or larger). This synthetic route is in competition with a reaction previously-reported by our group1, allowing the generation of a combinatorial library of tri-substituted purines by the simple modification of the amide and the alkoxide employed. Among the variety of structures generated, two purine analogues displayed trypanocidal activity against the protozoan parasite Trypanosoma brucei with IC50 , 5 mM, being each of those compounds obtained through each of the synthetic pathways.J.J.D.M. thanks Spanish Ministerio de Economı´a y Competitividad for a Ramon y Cajal Fellowship. A.U.B. thanks MRC IGMM for an academic fellowship. This work was partially supported by Grant SAF2011-30528 to J.A.G.S.

One-pot, regiospecific assembly of (E)-benzamidines from δ- and γ-amino acids via an intramolecular aminoquinazolinone rearrangement

The efficient generation of novel, N-linked benzamidines resulting from a regiospecific rearrangement of quinazolinones is described. This methodology study explored reaction parameters including the effect of changing solvent and temperature, as well as varying electronic substituents on the structural core. The transformation was extensively optimized in terms of reaction conditions and scope, resulting in a protocol that consistently affords diversely functionalized amidines in high yield. The process permits regional structural derivatization that was previously inaccessible, and the multistep process was also reduced to a telescoped, five-step sequence that efficiently affords pharmacologically unique (E)-benzamidoamidines from N-BOC protected γ- and δ-amino acids

Highly potent and isoform selective dual site binding tankyrase/Wnt signaling inhibitors that increase cellular glucose uptake and have antiproliferative activity

Abstract Compounds 𝟏𝟑 and 𝟏𝟒 were evaluated against eleven PARP isoforms to reveal that both 𝟏𝟑 and 𝟏𝟒 were more potent and isoform-selective towards inhibiting tankyrases (TNKSs) than the “standard” inhibitor 𝟏 (XAV939)⁵, i.e. IC₅₀ = 100 pM vs. TNKS2 and IC₅₀ = 6.5 μM vs. PARP1 for 𝟏𝟒. In cellular assays, 𝟏𝟑 and 𝟏𝟒 inhibited Wnt-signaling, enhanced insulin-stimulated glucose uptake and inhibited the proliferation of DLD-1 colorectal adenocarcinoma cells to a greater extent than 𝟏