Synthesis of a potent and selective inhibitor of p90 Rsk

[reaction: see text] The synthesis of the naturally occurring kaempferol glycoside SL0101 has been accomplished, as has its biochemical evaluation. SL0101 exhibits selective and potent p90 Rsk inhibitory activity at nanomolar concentrations without inhibiting the function of upstream kinases such as MEK, Raf, or PKC. The synthesis verified the structural assignment of the natural product and has provided access to material sufficient for detailed biological evaluation.     

Activation of p300 histone acetyltransferase by small molecules altering enzyme structure: probed by surface-enhanced Raman spectroscopy

Reversible acetylation of nucleosomal histones and nonhistone proteins play pivotal roles in the regulation of all the DNA templated phenomenon. Dysfunction of the enzymes involved in the acetylation/deacetylation leads to several diseases. Therefore, these enzymes are the targets for new generation therapeutics. Here, we report the synthesis of trifluoromethyl phenyl benzamides and their effect on histone acetyltransferase (HAT) activity of p300. One of these benzamides, CTPB (N-(4-chloro-3-trifluoromethyl-phenyl)-2-ethoxy-6-pentadecyl-benzamide), was discovered as a potent activator of the p300 HAT activity. We have found that pentadecyl hydrocarbon chain of CTPB is required to activate the HAT only under certain context. Furthermore, our results show that the relative position of -CF3 and -Cl in CTB (N-(4-chloro-3-trifluoromethyl-phenyl)-2-ethoxy-benzamide) is also very critical for the activation. Surface-enhanced Raman spectroscopy (SERS) of p300 and the HAT activator complexes evidently suggest that the activation of HAT activity is achieved by the alteration of p300 structure. Therefore, apart from elucidating the chemical basis for small molecule mediated activation of p300, this report also describes, for the first time, Raman spectroscopic analysis of the complexes of histone-modifying enzymes and their modulators, which may be highly useful for therapeutic applications.     

A potent and highly selective sulfotransferase inhibitor

In the present work, we have used a newly developed, fluorescence-based assay to screen a library of >30 000 compounds as potential beta-arylsulfotransferase-IV inhibitors. A total of 11 inhibitors were discovered. Most of the compounds discovered showed low micromolar inhibition, but one of the compounds showed potent inhibition (Ki = 96 nM). The most potent of these inhibitors was tested against a variety of other purine binding enzymes and showed remarkable specificity.     

Total synthesis of spiruchostatin A, a potent histone deacetylase inhibitor

The total synthesis of spiruchostatin A was accomplished, unambiguously confirming its structure. Key steps included the use of the Nagao thiazolidinethione auxiliary for a diastereoselective acetate aldol reaction and as an activated acylating agent for amide formation, and macrolactonization by the Yamaguchi protocol. Spiruchostatin A is shown to have biological activity similar to that of FK228, a potent histone deacetylase (HDAC) inhibitor in clinical trials. The spiruchostatin A analogue, epimeric at the beta-hydroxy acid, is inactive, highlighting the importance of stereochemistry at this position for interactions with HDACs.     

Autoacetylation induced specific structural changes in histone acetyltransferase domain of p300: probed by surface enhanced Raman spectroscopy

Reversible acetylation of histone and non-histone proteins plays an important role in the regulation of gene expression and cellular homeostasis. A balance between acetylation and deacetylation of these proteins are maintained by histone acetyltransferases (HATs) and histone deacetylases (HDACs). Among different HATs, p300/CBP is the most widely studied chromatin modifying enzymes. p300 is involved in several physiological processes like cell growth, regulation of gene expression, development, and tumor suppressor, and therefore its dysfunction causes different diseases. The autoacetylation of p300 is one of the key regulators of its catalytic activity. Mechanistically, autoacetylation induced structural changes in the p300 HAT domain acts as a master switch. In this report, we have shown that the natural HAT inhibitor garcinol could potently inhibit the autoacetylation activity. Furthermore, for the first time, we demonstrate that indeed autoacetylation induces structural changes in p300 HAT domain, as probed by surface-enhanced Raman scattering. Presumably, SERS will be a very useful tool to find out the structural changes in the other self-modifying enzymes like kinases and methyltransferases.     

Synthesis and NMR structure of p41icf,a potent inhibitor of human cathepsin L

The total synthesis and structural characterization of the MHCII-associated p41 invariant chain fragment (P41icf) is described. P41icf plays a crucial role in the maturation of MHC class II molecules and antigen processing, acting as a highly selective cathepsin L inhibitor. P41icf synthesis was achieved using a combined solid-phase/solution approach. The entire molecule (65 residues, 7246 Da unprotected) was assembled in solution from fully protected peptides in the size range of 10 residues. After deprotection, oxidative folding in carefully adjusted experimental conditions led to the completely folded and functional P41icf with a disulfide pairing identical to that of native P41icf. CD, NMR, and surface plasmon resonance (SPR) were used for the structural and functional characterization of synthetic P41icf. CD thermal denaturation showed clear cooperative behavior. Tight cathepsin L binding was demonstrated by SPR. (1)H NMR spectroscopy at 800 MHz of unlabeled P41icf was used to solve the three-dimensional structure of the molecule. P41icf behaves as a well-folded protein domain with a topology very close to the crystallographic cathepsin L-bound form.     

Enantioselective total synthesis of (+)-largazole, a potent inhibitor of histone deacetylase

An enantioselective total synthesis of the cytotoxic natural product (+)-largazole (1) is described. It is a potent histone deacetylase inhibitor. Our synthesis is convergent and involves the assembly of thiazole 3-derived carboxylic acid with amino ester 4 followed by cycloamidation of the corresponding amino acid. The synthesis features an efficient cross-metathesis, an enzymatic kinetic resolution of a beta-hydroxy ester, a selective removal of a Boc-protecting group, a HATU/HOAt-promoted cycloamidation reaction, and synthetic manipulations to a sensitive thioester functional group.     

KNI-272, a highly selective and potent peptidic HIV protease inhibitor

Kynostatin {KNI-272; systematic name: 3-[3-benzyl-2-hydroxy-9-(isoquinolin-5-yl­oxy)-6-methyl­sulfanyl­methyl-5,8-dioxo-4,7-di­aza­nonanoyl]-N-tert-butyl-1,3-thia­zolane-4-carbox­amide}, a highly selective and potent HIV protease inhibitor containing allo­phenyl­norstatin [(2S,3S)-3-amino-2-hydroxy-4-phenyl­butyric acid], has been crystallized as the hydrate, C₃₃H₄₁N₅O₆S₂·0.803H₂O, from aqueous hexyl­ene glycol. The observed disorder of the phenyl group in the structure is related to the mode of hydration. The backbone conformation of the mol­ecule is twisted and the overall conformation of the free inhibitor is similar to that observed in its complex with HIV protease.     

Total synthesis of spiruchostatin B, a potent histone deacetylase inhibitor, from a microorganism

The first total synthesis of spiruchostatin B, a potent histone deacetylase inhibitor, was achieved in a convergent manner; the synthesis established stereochemistry at the C5' position.     

Synthesis of streptolydigin, a potent bacterial RNA polymerase inhibitor

Streptolydigin is a highly potent, broad-spectrum antibiotic produced by Streptomyces lydicus, which inhibits bacterial RNA polymerase. We describe the first synthesis of streptolydigin, which was assembled in a highly convergent and fully stereocontrolled fashion with a longest linear sequence of 24 steps starting from commercially available precursors. The assembly process entailed preparation of fully elaborated streptolic and ydiginic subunits of the natural product, followed by a highly efficient union in a three-step one-pot procedure, which included Dieckmann cyclization with a concomitant imide opening, Horner-Wadsworth-Emmons olefination, and desilylation.     

Synthesis of SMP-797: a new potent ACAT inhibitor

A potent ACAT (acyl-CoA: cholesterol acyltransferase) inhibitor SMP-797 was effectively synthesized by the urea formation of 3-amino-4-aryl-1,8-naphthyridin-2(1H)-one and 4-amino-2,6-diisopropylamine. The synthesis of the former compound involved the Suzuki coupling reaction as a key step, and the latter was prepared by the 4-selective nitration of 2,6-diisopropylaniline using 2,3,5,6-tetrabromo-4-methyl-4-nitro-2,5-cyclohexadienone.     

A highly potent and selective PKCalpha inhibitor generated via combinatorial modification of a peptide scaffold

A potent and highly selective inhibitor of protein kinase C alpha has been generated via the combinatorial modification of a consensus sequence peptide. The inhibitor displays a Ki of 800 pM versus variable peptide substrate and good selectivity versus other members of the PKC family, including PKCbeta (385-fold), PKCgamma (580-fold), PKCdelta (2730-fold), PKCepsilon (600-fold), PKCeta (1310-fold), PKCtheta (1210-fold), PKCiota (940-fold), and PKCzeta (640-fold). The parallel synthesis strategy employed is easily automated and straightforward to implement.     

Total synthesis and biological mode of action of largazole: a potent class I histone deacetylase inhibitor

The efficient total synthesis of the recently described natural substance largazole (1) and its active metabolite largazole thiol (2) is described. The synthesis required eight linear steps and proceeded in 37% overall yield. It is demonstrated that largazole is a pro-drug that is activated by removal of the octanoyl residue from the 3-hydroxy-7-mercaptohept-4-enoic acid moiety to generate the active metabolite 2, which is an extraordinarily potent Class I histone deacetylase inhibitor. Synthetic largazole and 2 have been evaluated side-by-side with FK228 and SAHA for inhibition of HDACs 1, 2, 3, and 6. Largazole and largazole thiol were further assayed for cytotoxic activity against a panel of chemoresistant melanoma cell lines, and it was found that largazole is substantially more cytotoxic than largazole thiol; this difference is attributed to differences in the cell permeability of the two substances.     

Synthesis of a tetra-deuterium-labeled derivative of potent and selective anticancer agent AA005

Annonaceous acetogenins are a series of potent naturally occurring anticancer agents, which act as inhibitors of complex I in mitochondria. AA005, a mimicry of acetogenins, has been found as active as those natural products and to present high selectivities between cancer and normal cells. In order to investigate the further cell-based mechanism induced by AA005, a d⁴-labeled derivative of AA005 (AA005-d⁴) was designed to detect the drug permeation ability into the membranes. In this letter, the synthesis is reported of this deuterium-labeled compound, wherein a ethylene-d⁴ glycol unit is incorporated efficiently into the molecule skeleton by simple etherifications.     

Synthesis of a naphthyridone p38 MAP kinase inhibitor

Compound 1 is a p38 MAP kinase inhibitor potentially useful for the treatment of rheumatoid arthritis and psoriasis. A novel six-step synthesis suitable for large-scale preparation was developed in support of a drug development program at Merck Research Laboratories. The key steps include a tandem Heck-lactamization, N-oxidation, and a highly chemoselective Grignard addition of 4-(N-tert-butylpiperidinyl)magnesium chloride to a naphthyridone N-oxide. The N-oxide exerted complete chemoselectivity via chelation in directing the Grignard addition to the alpha position as opposed to 1,4-addition on the ene-lactam. The dihydropyridyl adduct was in situ aromatized with isobutylchloroformate followed by heating in pyridine. Syntheses of Grignard precursor, N-tert-butyl-4-chloro-piperidine, were accomplished via transamination with a quaternary ammonium piperidone or via addition of methylmagnesium chloride to an iminium ion. Utilizing this chemistry, multi-kilogram preparation of compound 1 was successfully demonstrated.     

Synthesis and evaluation of potent yaku'amide A analogs

Two full-length analogs of the anticancer peptide yaku''amide A (1a) and four partial structures have been synthesized. These analogs were identified by computational studies in which the three E- and Z-ΔIle residues of the natural product were replaced by the more accessible dehydroamino acids ΔVal and ΔEnv. Of the eight possible analogs, modeling showed that the targeted structures 2a and 2b most closely resembled the three-dimensional structure of 1a. Synthesis of 2a and 2b followed a convergent route that was streamlined by the absence of ΔIle in the targets. Screening of the compounds against various cancer cell lines revealed that 2a and 2b mimic the potent anticancer activity of 1a, thereby validating the computational studies.

Simplified full-length analogs of yaku''amide A were designed with the aid of computations and then synthesized. The analog that was predicted to most closely resemble the structure of the natural product mimicked its anticancer activity.     

Synthesis of 1,4,6-Trideoxy-1,4-imino-D-mannitol: a potent α-mannosidase inhibitor

The title trihydroxypyrrolidine 4, readily synthesized $\text{in one step}$ from the naturally occurring sugar D-perosamine, is ten times more active than swainsonine as a competitive inhibitor of jackbean α-mannosidase.     

Synthesis and biological evaluation of a new series of histone deacetylases inhibitors

Histone deacetylases （HDACs） play an important role in tumorigenesis. Inhibition of HDACs is considered as a potent strategy for cancer therapy. Two lead compounds （ja and jb） were found to have activities against HDACs with IC50 at about 15 μmol/L. Then a new series of hydroximic acid derivatives were designed and synthesized based on them. The HDACs activity assay in vitro found that compounds J04 and ,109 are nearly as potent as the positive control drug Zolinza.