A straightforward total synthesis of (-)-chaetominine.

A total synthesis of the tripeptide alkaloid (-)-chaetominine (1) was achieved in 9.3% overall yield starting from commercially available D-tryptophan methyl ester, based on a short and straightforward (nine steps) sequence. The early stage introduction (first step) of the quinazolinone moiety and the late stage introduction (penultimate step) of the hydroxy group allowed a synthetic strategy devoid of protective groups. The key step of the process is the a-c tricyclic ring construction via an unprecedented NCS-mediated N-acyl cyclization on an indole ring to give tetrahydro-1H-pyrido[2,3-b]indole 11. In the penultimate step, oxidation of the tetracyclic intermediate 14 with oxaziridine 15 gave only one of the four possible diastereoisomers, the cis-diastereoisomer 16 resulting from the attack of the oxaziridine to the double bond face opposite to the c-d ring substituents. In the last step, the complete stereocontrol of the Et(3)SiH/TFA reduction of compound 16, probably involving a N-acyliminium ion, can be attributed to ring constrain, which forces the b-c ring junction in the more stable cis-orientation. (-)-Chaetominine (1) showed a negligible inhibitory activity on several cancer cell lines.

Improved synthesis of polyfluorinated L-lysine for 19F NMR-based screening.

Polyfluorinated N-alpha-Fmoc-is an element of-Boc-L-lysine represents the best-in-class among a set of polyfluorinated amino acids (PFAs) which are useful tools for (19)F NMR-Based Screening. In this communication, optimized reaction conditions that allowed for the multi-gram preparation of this unnatural amino acid are reported.

A submarine journey: the pyrrole-imidazole alkaloids.

In his most celebrated tale "The Picture of Dorian Gray", Oscar Wilde stated that "those who go beneath the surface do so at their peril". This sentence could be a prophetical warning for the practitioner who voluntarily challenges himself with trying to synthesize marine sponge-deriving pyrrole-imidazole alkaloids. This now nearly triple-digit membered community has been growing exponentially in the last 20 years, both in terms of new representatives and topological complexity--from simple, achiral oroidin to the breathtaking 12-ring stylissadines A and B, each possessing 16 stereocenters. While the biosynthesis and the role in the sponge economy of most of these alkaloids still lies in the realm of speculations, significant biological activities for some of them have clearly emerged. This review will account for the progress in achieving the total synthesis of the more biologically enticing members of this class of natural products.

Synthesis and endosomolytic properties of poly(amidoamine) block copolymers.

The poly(amidoamine)s (PAAs) ISA 1 and ISA 23 display pH-dependent conformational change and pH-dependent membrane perturbation. These properties confer potential for use as endosomolytic polymers for intracytoplasmic delivery of toxins and genes. Both polymers are relatively non-toxic, and moreover ISA 23 has the beneficial property in vivo, of being non hepatotropic when administered intravenously. Although ISA 23 and ISA 1 demonstrate ability to transfect cells, ISA 1 is also able to promote intracellular delivery of non-permeant toxins. The aim of this study was to synthesise random and block copolymers of ISA 1 and ISA 23 and investigate whether these second generation hybrids would allow optimisation of PAA biological characteristics. Random and block copolymers of ISA 1 and ISA 23 were synthesised by hydrogen transfer polyaddition to generate a library of PAAs with an ISA 23:ISA 1 molar ratios of 2:1 to 4:1. The resultant polymers have a pI slightly below 7.4 and a M(w) of 19,900-49,000 g/mol and a M(n) of 13,100-24,100 g/mol. Whereas none of the random or block copolymers were haemolytic at pH 7.4 all demonstrated pH-dependent membrane activity. At pH 5.5 they caused 50-60% haemoglobin (Hb) release over 1 h. This was slightly less than that seen for ISA 23 (80% Hb release). None of the copolymers were cytotoxic against B16F10 cells during a 72 h incubation (IC(50) > 2 mg/ml; MTT assay). The ability of the random and block copolymer PAAs to deliver the toxin gelonin was also examined, but only ISA 1 and the block copolymer B2 (ISA 23:ISA 1 at a 2:1 molar ratio) were able to promote intracellular delivery, as measured by cytotoxic activity. It would be interesting to study the body distribution of B2 and determine whether this toxin-delivering PAA is able to escape liver capture.

Discovery of 2-(cyclohexylmethylamino)pyrimidines as a new class of reversible valosine containing protein inhibitors.

Valosine-containing protein (VCP), also known as p97 or cdc48 in yeast, is a highly abundant protein belonging to the AAA ATPase family involved in a number of essential cellular functions, including ubiquitin-proteasome mediated protein degradation, Golgi reassembly, transcription activation, and cell cycle control. Altered expression of VCP has been detected in many cancer types sometimes associated with poor prognosis. Furthermore, VCP mutations are causative of some neurodegenerative disorders. In this paper we report the discovery, synthesis, and structure-activity relationships of substituted 2-aminopyrimidines, representing a new class of reversible VCP inhibitors. This class of compounds, identified in a HTS campaign against recombinant VCP, has been progressively expanded and manipulated to increase biochemical potency and gain cellular activity.

Alkylsulfanyl-1,2,4-triazoles, a new class of allosteric valosine containing protein inhibitors. Synthesis and structure-activity relationships.

Valosine containing protein (VCP), also known as p97, is a member of AAA ATPase family that is involved in several biological processes and plays a central role in the ubiquitin-mediated degradation of misfolded proteins. VCP is an ubiquitously expressed, highly abundant protein and has been found overexpressed in many tumor types, sometimes associated with poor prognosis. In this respect, VCP has recently received a great deal of attention as a potential new target for cancer therapy. In this paper, the discovery and structure-activity relationships of alkylsulfanyl-1,2,4-triazoles, a new class of potent, allosteric VCP inhibitors, are described. Medicinal chemistry manipulation of compound 1, identified via HTS, led to the discovery of potent and selective inhibitors with submicromolar activity in cells and clear mechanism of action at consistent doses. This represents a first step toward a new class of potential anticancer agents.

Poly(amidoamine) salt form: effect on pH-dependent membrane activity and polymer conformation in solution.

On exposure to an acidic pH, linear poly(amidoamine)s (PAAs) cause membrane perturbation and consequently have potential as endosomolytic polymers for the intracellular delivery of genes and toxins. Previous studies used PAAs in the hydrochloride form only. The aim of this study was to investigate systematically the effect of the PAA counterion on pH-dependent membrane activity, general cytotoxicity, and PAA solution properties to help guide optimization of PAA structure for further development of PAA-protein conjugates. PAAs (ISA 1, 4, 22, and 23; M(w) 10000-50000 g/mol) were synthesized to provide a library of PAAs having different counterions including the acetate, citrate, hydrochloride, lactate, phosphate, and sulfate salts. pH-Dependent membrane activity was assessed using a rat red blood cell haemolysis assay (conducted at a starting pH of 7.4, 6.5, or 5.5; 1 mg/mL; 1 h), and general cytotoxicity was investigated using a murine melanoma cell line (B16F10) and a human bladder endothelial-like cell line (ECV-304). Whereas poly(ethyleneimine) was haemolytic at the starting pH of 7.4 at 1 h [ approximately 50% haemoglobin (Hb) release], none of the PAA salts were haemolytic at a starting pH of 7.4 or 6.5. Although PAA acetate, citrate, and lactate were also non-haemolytic at the starting pH of 5.5, the sulfate and hydrochloride forms caused significant haemolysis (up to 80% Hb release) and ISA 22 and 23 phosphate were also markedly haemolytic ( approximately 70% Hb release). These counterion-specific differences were also clearly visible using scanning electron microscopy, which was used to visualize the red blood cell morphology. All PAAs were relatively nontoxic (IC(50) >or= 300-5000 microg/mL) compared to poly-l-lysine (IC(50) = 2-10 microg/mL), the PAA hydrochloride salts produced the greatest cytotoxicity, and the B16F10 cells were more sensitive than the ECV-304 cells. Small-angle neutron scattering suggested that ISA 23 hydrochloride had a larger hydrodynamic radius (5.1 +/- 0.2 nm) than the citrate salt (3.1 +/- 0.2 nm). These results provide indirect evidence for the salt- and pH-dependent changes in the conformation of the polymer coil. This study clearly demonstrates the importance of optimization of the counterion form when developing endosomolytic polymers designed to mediate pH-dependent membrane permeabilization.