Guanidino quinazolines and pyrimidines promote readthrough of premature termination codons in cells with native nonsense mutations.

Using small molecules to induce readthrough of premature termination codons is a promising therapeutic approach to treating genetic diseases and cancers caused by nonsense mutations, as evidenced by the widespread use of ataluren to treat nonsense mutation Duchene muscular dystrophy. Herein we describe a series of novel guanidino quinazoline and pyrimidine scaffolds that induce readthrough in both HDQ-P1 mammary carcinoma cells and mdx myotubes. Linkage of basic, tertiary amines with aliphatic, hydrophobic substituents to the terminal guanidine nitrogen of these scaffolds led to significant potency increases. Further potency gains were achieved by flanking the pyrimidine ring with hydrophobic substituents, inducing readthrough at concentrations as low as 120 nM and demonstrating the potential of these compounds to be used either in combination with ataluren or as stand-alone therapeutics.

Unexpected Observation of the Dimroth Rearrangement in the Ribosylation of 4-Aminopyrimidines.

A method for the preparation of 1-(N-ribofuranosyl)-6-imino-1,6-dihydropyrimidin-4-amines 3 or 4-(N-ribofuranosyl)-6-aminopyrimidines 4 via glycosylation of 4-aminopyrimidines 2 or 5 is described. Silylated 4-aminopyrimidines 2 or 5 upon ribosylation with 1 provide products 3. When intermediates 3 contain a strongly electron-withdrawing group, such as C(4)-Cl or C(5)-NO2, they rearrange to products 4 in the presence of aqueous ammonia. A mechanism is proposed that involves a ring-opening/ring-closing (Dimroth) rearrangement.

SAR studies toward discovery of emvododstat (PTC299), a potent dihydroorotate dehydrogenase (DHODH) inhibitor.

Dihydroorotate dehydrogenase (DHODH) is the enzyme that catalyzes a rate-determining step during the de novo synthesis of uridine, an important source of cellular pyrimidine nucleotides. Ability to modulate the activity of this enzyme may be used to control diseases associated with rapid, out-of-control cell growth in oncology, immunology, and virology. Emvododstat (PTC299) is a tetrahydro-ß-carboline DHODH inhibitor discovered through the GEMS technology (Gene Expression Modulation by Small-Molecules). Described in this paper is the lead optimization campaign that culminated in the discovery of this highly potent DHODH inhibitor.

Chemical modifications of G418 (geneticin): Synthesis of novel readthrough aminoglycosides results in an improved in vitro safety window but no improvements in vivo.

G418 is currently the most potent and active aminoglycoside to promote readthrough of eukaryotic nonsense mutations. However, owing to its toxicity G418 cannot be used in vivo to study readthrough activity A robust and scalable method for selective derivatization of G418 was developed to study the biological activity and toxicity of a series of analogs. Despite our synthetic efforts, an improvement in readthrough potency was not achieved. We discovered several analogs that demonstrated reduced zebra fish hair cell toxicity (a surrogate for ototoxicity), but this reduction in cellular toxicity did not translate to reduced in vivo toxicity in rats.

Tandem double intramolecular [4+2]/[3+2] cycloadditions of nitroalkenes: construction of the pentacyclic core structure of daphnilactone B.

An asymmetric synthesis of the ABCD ring system of daphnilactone B is described. The synthesis features a tandem, double intramolecular, [4+2]/[3+2] cycloaddition of a highly functionalized, enantiomerically enriched nitroalkene to generate a pentacyclic nitroso acetal. The cycloaddition establishes six contiguous stereogenic centers including the critical CD ring junction that bears two quaternary stereogenic centers. Hydrogenolysis of the nitroso acetal followed by amide reduction and cyclization provided the AB rings. The methyl substituent on the A ring was installed in the correct configuration via hydrogenation of an exocyclic olefin in the final step.

ASYMMETRIC SYNTHESIS OF THE ABCD RING SYSTEM OF DAPHNILACTONE B VIA A TANDEM, DOUBLE INTRAMOLECULAR, [4+2]/[3+2] CYCLOADDITION STRATEGY.

An asymmetric synthesis of the ABCD ring system of daphnilactone B is described. The synthesis features a tandem, double intramolecular, [4+2]/[3+2] cycloaddition of a highly functionalized, enantiomerically enriched nitroalkene to generate a pentacyclic nitroso acetal. The cycloaddition establishes six contiguous stereogenic centers including the critical CD ring junction that bears two quaternary stereogenic centers. Hydrogenolysis of the nitroso acetal followed by amide reduction and cyclization provided the AB rings. The methyl substituent on the A ring was installed in the correct configuration via hydrogenation of an exocyclic olefin in the final step.

Intramolecular [4 + 2] cycloaddition of nitroalkenes for construction of vicinal quaternary stereocenters.

[chemical reaction: see text]. Nitroalkene (E)-1 has been synthesized to test the feasibility of an intramolecular [4 + 2] cycloaddition in a planned synthesis of daphnilactone B. This nitro olefin contains two unique structural features, a nitromethylene lactone and a pendant diene, that combine under the action of SnCl4 in a highly selective fashion to afford nitronates 2a and 2b. These products represent the correct relationship for the vicinal quaternary stereogenic centers in the core of daphnilactone B.

Tandem double-intramolecular [4+2]/[3+2] cycloadditions of nitroalkenes. Studies toward a total synthesis of daphnilactone B: piperidine ring construction.

[reaction: see text] Two model studies in support of a total synthesis of the complex polycyclic alkaloid daphnilactone B have been completed. The objectives of the models studies were to demonstrate the use of a tandem double-intramolecular [4+2]/[3+2] nitroalkene cycloaddition for the stereocontrolled construction of four of the rings in the core of the natural product. The first model study established the ability to create a pyrrolidine ring corresponding to ring A of daphnilactone B through a modification of the dipolarophile and subsequent functional group manipulations. The second model study required the modification of the dienophile in the [4+2] cycloaddition to accommodate the formation of a piperidine ring (ring B of daphnilactone B). Nitroalkene 26 containing a diene as the dienophile served well in the tandem cycloaddition to afford the nitroso acetal 38a in 77% yield. Subsequent functional group manipulations allowed for the high-yielding conversion to the core of daphnilactone B.