Haloperidol Metabolite II Valproate Ester (S)-(-)-MRJF22: Preliminary Studies as a Potential Multifunctional Agent Against Uveal Melanoma.

Increased angiogenesis and vascular endothelial growth factor (VEGF) levels contribute to higher metastasis and mortality in uveal melanoma (UM), an aggressive malignancy of the eye in adults. (±)-MRJF22, a prodrug of the sigma (σ) ligand haloperidol metabolite II conjugated with the histone deacetylase (HDAC) inhibitor valproic acid, has previously demonstrated a promising antiangiogenic activity. Herein, the asymmetric synthesis of (R)-(+)-MRJF22 and (S)-(-)-MRJF22 was performed to investigate their contribution to (±)-MRJF22 antiangiogenic effects in human retinal endothelial cells (HREC) and to assess their therapeutic potential in primary human uveal melanoma (UM) 92-1 cell line. While both enantiomers displayed almost identical capabilities to reduce cell viability than the racemic mixture, (S)-(-)-MRJF22 exhibited the highest antimigratory effects in endothelial and tumor cells. Given the fundamental contribution of cell motility to cancer progression, (S)-(-)-MRJF22 may represent a promising candidate for novel antimetastatic therapy in patients with UM.

Inactivation Mechanism of Neuronal Nitric Oxide Synthase by (S)-2-Amino-5-(2-(methylthio)acetimidamido)pentanoic Acid: Chemical Conversion of the Inactivator in the Active Site.

Neuronal nitric oxide synthase (nNOS) is one of the three isoforms of nitric oxide synthase (NOS). The other two isoforms include inducible NOS (iNOS) and endothelial NOS (eNOS). These three isoforms of NOS are widely present in both human and other mammals and are responsible for the biosynthesis of NO. As an essential biological molecule, NO plays an essential role in neurotransmission, immune response, and vasodilation; however, the overproduction of NO can cause a series of diseases. Thus, the selective inhibition of three isoforms of NOS has been considered to be important in treating related diseases. The active sites of the three enzymes are highly conserved, causing the selective inhibition of the three enzymes to be a great challenge. (S)-2-Amino-5-(2-(methylthio)acetimidamido)pentanoic acid (1) has been experimentally proved to be a selective and time-dependent irreversible inhibitor of nNOS, and three pathways, including sulfide oxidation, oxidative dethiolation, and oxidative demethylation, have been suggested. In this work, we performed quantum mechanics/molecular mechanics calculations to verify the chemical conversion of inactivator 1. Although we agree with the previously suggested chemical transformation process, our calculations demonstrated that there are lower energy pathways to accomplish both oxidative dethiolation and oxidative demethylation. These three branching reactions are competitive, but only dethiolation and demethylation reactions can generate inhibitory intermediates. As a powerful time-dependent irreversible inhibitor of nNOS, the key sulfur atom and middle imine are all necessary. Our calculation results not only verified the chemical reaction of inhibitor 1 occurring in the enzymatic active site but also explained the inactivation mechanism of inhibitor 1. This is also the first verified example of the heme-enzyme-catalyzed S-demethylation mechanism.

Synthesis and in-vitro anti-cancer evaluations of multi-methoxylated asymmetrical diarylpentanoids as intrinsic apoptosis inducer against colorectal cancer.

In the present study, a series of nine stable 3,4,5-methoxylphenyl-containing asymmetrical diarylpentanoids, derivatives of curcuminoids, have been synthesized, characterized and evaluated for their in-vitro anti-cancer potential against a panel of BRAF- and KRAS-mutated colorectal cancer cell lines including T84, LoVo and SW620, HT29, RKO and NCI-H508, respectively. Structure-activity relationship study on cytotoxicity of tested compounds suggested that the presence of meta-hydroxyl and adjacent dimethoxyl groups are crucial for enhanced cytotoxicity of diarylpentanoids. Among the evaluated analogs, 8 has been identified as the lead compound due to its highest chemotherapeutic index of 9.9 and nano molar scale cytotoxicity against SW620 and RKO. Colonies formation and cell cycle analyses on 8-treated RKO cells showed that 8 exhibits strong anti-proliferative activity by inducing G2/M-phase cell arrest. Subsequent flow cytometry based annexin-V and DCFHDA studies suggested that 8 could induce apoptosis through intracellular ROS-dependent pathway. Further Western blot studies confirmed that 8 has induced intrinsic apoptosis in RKO cells through the up-regulations of Bad and Bax pro-apoptotic proteins and down-regulations of Bcl-2 and Bcl-xL pro-survival proteins. In all, the present results suggest that 8 could be a potent lead which deserves further modification and investigation in the development of small molecule-based anti-colorectal cancer agents.

Enzyme Degassing for Oxygen-Sensitive Reactions in Open Vessels of an Automated Parallel Synthesizer: RAFT Polymerizations.

An enzyme degassing method for oxygen-intolerant polymerizations was implemented in a commercially available automated parallel synthesizer and tested for reversible addition-fragmentation chain transfer (RAFT) polymerizations performed in open vessels. For this purpose, a recently reported methodology that employs the enzyme glucose oxidase (GOx) to deplete oxygen in reaction media was utilized. The effectiveness of this approach to perform unattended parallel polymerization reactions in open vessels was demonstrated by comparing experimental results to those obtained under similar experimental conditions but utilizing the common degassing method of sparging N2 to remove oxygen. The proposed experimental technique displayed good precision in performing RAFT polymerizations and good control of the obtained polymers and could be easily adapted to other systems where the removal of oxygen is mandatory. This alternative high-throughput/high-output method may have the potential to increase productivity in research projects where oxygen-intolerant reactions are involved.

Synthesis, anticancer activity, structure-activity relationship and binding mode of interaction studies of substituted pentanoic acids.

Aim: Simultaneous inhibition of MMP-2 and HDAC8 may be an effective strategy to target cancer. Methodology: In continuation of our earlier efforts, a series of substituted pentanoic acids (1-18) were synthesized and checked for their biological activity along with some earlier reported compounds (19-35). Results: Compounds 18 and 31 were found to induce apoptosis effectively in a dose-dependent fashion in Jurkat-E6.1 cell line. They reduced the expression of both MMP-2 and HDAC8 effectively. 31 also produced prominent intensity of fluorescence to bring nick in Jurkat-E6.1 cells. 31 also showed cellular arrest in sub-G0 phase. Conclusion: Such compounds may be useful to battle against cancer.

Phenyl-γ-valerolactones and phenylvaleric acids, the main colonic metabolites of flavan-3-ols: synthesis, analysis, bioavailability, and bioactivity.

Covering: 1958 to June 2018 Phenyl-γ-valerolactones (PVLs) and their related phenylvaleric acids (PVAs) are the main metabolites of flavan-3-ols, the major class of flavonoids in the human diet. Despite their presumed importance, these gut microbiota-derived compounds have, to date, in terms of biological activity, been considered subordinate to their parent dietary compounds, the flavan-3-ol monomers and proanthocyanidins. In this review, the role and prospects of PVLs and PVAs as key metabolites in the understanding of the health features of flavan-3-ols have been critically assessed. Among the topics covered, are proposals for a standardised nomenclature for PVLs and PVAs. The formation, bioavailability and pharmacokinetics of PVLs and PVAs from different types of flavan-3-ols are discussed, taking into account in vitro and animal studies, as well as inter-individual differences and the existence of putative flavan-3-ol metabotypes. Synthetic strategies used for the preparation of PVLs are considered and the methodologies for their identification and quantification assessed. Metabolomic approaches unravelling the role of PVLs and PVAs as biomarkers of intake are also described. Finally, the biological activity of these microbial catabolites in different experimental models is summarised. Knowledge gaps and future research are considered in this key area of dietary (poly)phenol research.

A pentanoic acid derivative targeting matrix metalloproteinase-2 (MMP-2) induces apoptosis in a chronic myeloid leukemia cell line.

Depending on our previous observations, some compounds of pentanoic acid were designed and synthesized. Characterization of the synthesized compounds was done by mass, NMR and IR spectroscopy as well as elemental analysis. Among the synthesized molecules, (2S)-5-oxo-2-[(nitrobenzene-4-yl sulfonyl) amino]-5-(pentylamino) pentanoic acid (Cpd 11) was found as a lead and potent inhibitor of matrix metalloproteinase-2 (MMP-2). Molecular modeling and enzyme inhibition studies were done to confirm the interaction or inhibitory potential of this compound. Thereafter, the biological screening was done through cytotoxicity, anti-invasion and apoptosis-related assays. Docking analysis revealed that Cpd 11 interacted with the target molecule MMP-2 and with MMP-9. However, enzyme inhibition assay showed 3-fold MMP-2 inhibition compared to MMP-9. Cytotoxicity assay showed the inhibitory potential of Cpd 11 against K562 cell line having IC50 value of 17.9 ± 0.01 µM after 48 h of incubation. The cell death was apoptotic in nature as revealed from the annexin V and sub-G1 cell cycle arrest assay. Besides this, Cpd 11 also exhibited dose dependent anti-invasive activity into K562 cell line. On the other hand, flow cytometry and western blot data revealed Cpd 11 induced downregulation of MMP-2 in K562 cell line after 48 h of incubation that might be linked with the anti-invasive and apoptotic activity furthermore. Therefore, the overall results validated each method and make this molecule as a potent MMP-2 inhibitor that blocked the invasion and could bring apoptosis at later stages in K562 cells sparing the normal ones.

Metal-Chelate Immobilization of Lipase onto Polyethylenimine Coated MCM-41 for Apple Flavor Synthesis.

An enzyme immobilized on a mesoporous silica nanoparticle can serve as a multiple catalyst for the synthesis of industrially useful chemicals. In this work, MCM-41 nanoparticles were coated with polyethylenimine (MCM-41@PEI) and further modified by chelation of divalent metal ions (M = Co2+, Cu2+, or Pd2+) to produce metal-chelated silica nanoparticles (MCM-41@PEI-M). Thermomyces lanuginosa lipase (TLL) was immobilized onto MCM-41, MCM-41@PEI, and MCM-41@PEI-M by physical adsorption. Maximum immobilization yield and efficiency of 75 ± 3.5 and 65 ± 2.7% were obtained for MCM@PEI-Co, respectively. The highest biocatalytic activity at extremely acidic and basic pH (pH = 3 and 10) values were achieved for MCM-PEI-Co and MCM-PEI-Cu, respectively. Optimum enzymatic activity was observed for MCM-41@PEI-Co at 75 °C, while immobilized lipase on the Co-chelated support retained 70% of its initial activity after 14 days of storage at room temperature. Due to its efficient catalytic performance, MCM-41@PEI-Co was selected for the synthesis of ethyl valerate in the presence of valeric acid and ethanol. The enzymatic esterification yield for immobilized lipase onto MCM-41@PEI-Co was 60 and 53%, respectively, after 24 h of incubation in n-hexane and dimethyl sulfoxide media. Graphical Abstract Divalent metal chelated polyethylenimine coated MCM-41 (MCM-41@PEI-M) was used for immobilization of Thermomyces lanuginosa lipase catalyzing green apple flavor preparation.

Biarylalkyl Carboxylic Acid Derivatives as Novel Antischistosomal Agents.

Parasitic platyhelminths are responsible for serious infectious diseases, such as schistosomiasis, which affect humans as well as animals across vast regions of the world. The drug arsenal available for the treatment of these diseases is limited; for example, praziquantel is the only drug currently used to treat ≥240 million people each year infected with Schistosoma spp., and there is justified concern about the emergence of drug resistance. In this study, we screened biarylalkyl carboxylic acid derivatives for their antischistosomal activity against S. mansoni. These compounds showed significant influence on egg production, pairing stability, and vitality. Tegumental lesions or gut dilatation was also observed. Substitution of the terminal phenyl residue in the biaryl scaffold with a 3-hydroxy moiety and derivatization of the terminal carboxylic acid scaffold with carboxamides yielded compounds that displayed significant antischistosomal activity at concentrations as low as 10 µm with satisfying cytotoxicity values. The present study provides detailed insight into the structure-activity relationships of biarylalkyl carboxylic acid derivatives and thereby paves the way for a new drug-hit moiety for fighting schistosomiasis.

Synthesis of Resveratrol Derivatives and In Vitro Screening for Potential Cancer Chemopreventive Activities.

New resveratrol (trans-3,4',5-trihydroxystilbene) analogs were synthesized and screened for their in vitro cancer chemopreventive potential using various bioassays relevant for the prevention of carcinogenesis in humans: two assays to detect modulators of carcinogen metabolism (Cyp1A inhibition; determination of NAD(P)H/quinone reductase (QR) activity), three assays to identify radical scavenging and antioxidant properties (DPPH, ORAC, superoxide anion radicals in differentiated HL-60 cells), four assays to determine anti-inflammatory and anti-hormonal effects (iNOS, Cox-1 and aromatase inhibition, anti-estrogenic potential). 3,4',5-Tri-O-methyl resveratrol 1a was about sevenfold more active than resveratrol in inhibiting Cyp1A activity, it was a potent inducer of QR activity, and it showed pure anti-estrogenic activity (whereas resveratrol is a known mixed estrogen (ant)agonist with both estrogenic and anti-estrogenic properties). Dual estrogen ant-/agonist activity was restored in the mono-O-benzyl-substituted derivatives 4b (4'-O-benzyl resveratrol) and 5b (3-O-benzyl resveratrol). With respect to aromatase inhibition (Cyp19), which provided the highest number of actives, the benzyl-substituted series was more potent than the methyl-substituted derivatives of resveratrol, and 3-O-benzyl resveratrol 5b was about eightfold more active than resveratrol. Overall, 3,4',5-tri-O-pivaloyl resveratrol oxide 7c was identified as a potent inducer of phase 2 enzymes concomitant with inhibition of LPS-mediated iNOS induction.

[(18)F]Fluorobenzoyllysinepentanedioic Acid Carbamates: New Scaffolds for Positron Emission Tomography (PET) Imaging of Prostate-Specific Membrane Antigen (PSMA).

Radiolabeled urea-based low-molecular weight inhibitors of the prostate-specific membrane antigen (PSMA) are under intense investigation as imaging and therapeutic agents for prostate and other cancers. In an effort to provide agents with less nontarget organ uptake than the ureas, we synthesized four (18)F-labeled inhibitors of PSMA based on carbamate scaffolds. 4-Bromo-2-[(18)F]fluorobenzoyllysineoxypentanedioic acid (OPA) carbamate [(18)F]23 and 4-iodo-2-[(18)F]fluorobenzoyllysine OPA carbamate [(18)F]24 in particular exhibited high target-selective uptake in PSMA+ PC3 PIP tumor xenografts, with tumor-to-kidney ratios of >1 by 4 h postinjection, an important benchmark. Because of its high tumor uptake (90% injected dose per gram of tissue at 2 h postinjection) and high tumor-to-organ ratios, [(18)F]23 is promising for clinical translation. Prolonged tumor-specific uptake demonstrated by [(18)F]24, which did not reach equilibrium during the 4 h study period, suggests carbamates as alternative scaffolds for mitigating dose to nontarget tissues.

Divergent Synthesis of α,γ-Disubstituted γ-Butyrolactones through Diastereoselective Bromolactonization with Alkali Metal Bromide: Asymmetric Total Synthesis of (+)-Dubiusamine C.

A divergent synthesis of α-substituted bromomethyl γ-lactones was developed, which involves the diastereoselective bromolactonization of α-substituted 4-pentenoic acids and 4-pentenamides via umpolung of bromide by use of alkali metal bromide and Oxone (potassium peroxymonosulfate mixture, 2KHSO5·KHSO4·K2SO4) to obtain mainly cis-products from α-substituted 4-pentenoic acids and trans-products from α-substituted 4-pentenamides, and it was found that the bromonium species generated from KBr and Oxone had higher activity than N-bromosuccinimide. Furthermore, the asymmetric total synthesis of (+)-dubiusamine C, which was isolated as a minor diastereomer from Pandanus dubius, was accomplished for the first time through the cis-selective bromolactonization of (S)-α-methyl-4-pentenoic acid in nine linear steps and 36% overall yield.

Mechanism of Inactivation of Neuronal Nitric Oxide Synthase by (S)-2-Amino-5-(2-(methylthio)acetimidamido)pentanoic Acid.

Nitric oxide synthase (NOS) catalyzes the conversion of l-arginine to l-citrulline and the second messenger nitric oxide. Three mechanistic pathways are proposed for the inactivation of neuronal NOS (nNOS) by (S)-2-amino-5-(2-(methylthio)acetimidamido)pentanoic acid (1): sulfide oxidation, oxidative dethiolation, and oxidative demethylation. Four possible intermediates were synthesized. All compounds were assayed with nNOS, their IC50, KI, and kinact values were obtained, and their crystal structures were determined. The identification and characterization of the products formed during inactivation provide evidence for the details of the inactivation mechanism. On the basis of these studies, the most probable mechanism for the inactivation of nNOS involves oxidative demethylation with the resulting thiol coordinating to the cofactor heme iron. Although nNOS is a heme-containing enzyme, this is the first example of a NOS that catalyzes an S-demethylation reaction; the novel mechanism of inactivation described here could be applied to the design of inactivators of other heme-dependent enzymes.

Synthesis, Radiolabeling, and Biological Evaluation of (R)- and (S)-2-Amino-5-[(18)F]fluoro-2-methylpentanoic Acid ((R)-, (S)-[(18)F]FAMPe) as Potential Positron Emission Tomography Tracers for Brain Tumors.

A novel (18)F-labeled α,α-disubstituted amino acid-based tracer, 2-amino-5-[(18)F]fluoro-2-methylpentanoic acid ([(18)F]FAMPe), has been developed for brain tumor imaging with a longer alkyl side chain than previously reported compounds to increase brain availability via system L amino acid transport. Both enantiomers of [(18)F]FAMPe were obtained in good radiochemical yield (24-52% n = 8) and high radiochemical purity (>99%). In vitro uptake assays in mouse DBT gliomas cells revealed that (S)-[(18)F]FAMPe enters cells partly via sodium-independent system L transporters and also via other nonsystem A transport systems including transporters that recognize glutamine. Biodistribution and small animal PET/CT studies in the mouse DBT model of glioblastoma showed that both (R)- and (S)-[(18)F]FAMPe have good tumor imaging properties with the (S)-enantiomer providing higher tumor uptake and tumor to brain ratios. Comparison of the SUVs showed that (S)-[(18)F]FAMPe had higher tumor to brain ratios compared to (S)-[(18)F]FET, a well-established system L substrate.

Biosynthesis, characterization, and hemostasis potential of tailor-made poly(3-hydroxybutyrate-co-3-hydroxyvalerate) produced by Haloferax mediterranei.

We report the biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) random copolymers (R-PHBV) or higher-order copolymers (O-PHBV) in Haloferax mediterranei, with adjustable 3-hydroxyvalerate (3HV) incorporation by cofeeding valerate with glucose. Their microchemical structure, molecular weight and its distribution, and thermal and mechanical properties were characterized by NMR, GPC, DSC, TGA, and universal testing machine, respectively. (13)C NMR studies showed that O-PHBV copolymers consisted of short segments of PHB and PHV covalently linked together with random PHBV segments. Consistently, two Tg were observed in the DSC curves of O-PHBV. The "blocky" feature of O-PHBV enhanced crystallinity percentages and improved Young's modulus. Notably, the film of one O-PHBV copolymer, O-PHBV-1, showed unique foveolar cluster-like surface morphology with high hydrophobicity and roughness, as characterized using static contact angle and SEM and AFM analyses. It also exhibited increased platelet adhesion and accelerated blood clotting. The excellent hemostatic properties endow this copolymer with great potential in wound healing.

Air-stable solid aryl and heteroaryl organozinc pivalates: syntheses and applications in organic synthesis.

A wide range of air-stable, solid, polyfunctional aryl and heteroarylzinc pivalates were efficiently prepared by either magnesium insertion or Hal/Mg exchange followed by transmetalation with Zn(OPiv)2 (OPiv = pivalate). By reducing the amount of LiCl the air stability could be significantly enhanced compared with previously prepared reagents. An alternative route is directed magnesiation using TMPMgCl⋅LiCl (TMP = 2,2,6,6-tetramethylpiperidyl) followed by transmetalation with Zn(OPiv)2 or, for very sensitive substrates, direct zincation by using TMPZnOPiv. These zinc reagents not only show excellent stability towards air, but they also undergo a broad range of C-C bond-formation reactions, such as allylation and carbocupration reactions, as well as addition to aldehydes and 1,4-addition reactions. Acylation reactions can be performed by using an excess of TMSCl to overcome side reactions of the omnipresent pivalate anion.

Novel PPAR pan agonist, ZBH ameliorates hyperlipidemia and insulin resistance in high fat diet induced hyperlipidemic hamster.

Effective and safe pharmacological interventions for hyperlipidemia remains badly needed. By incorporating the key pharmacophore of fibrates into the natural scaffold of resveratrol, a novel structural compound ZBH was constructed. In present study, we found ZBH reserved approximately one third of the sirtuin 1 (SIRT1) activation produced by resveratrol at in-vitro enzyme activity assay, directly bound to and activated all three peroxisome proliferator-activated receptor (PPAR) subtypes respectively in PPAR binding and transactivation assays. Moreover, ZBH (EC50, 1.75 µM) activate PPARα 21 fold more efficiently than the well-known PPAR pan agonist bezafibrate (EC50 37.37 µM) in the cellular transactivation assays. In the high fat diet induced hyperlipidemic hamsters, 5-week treatment with ZBH significantly lowered serum triglyceride, total cholesterol, LDL-C, FFA, hyperinsulinemia, and improved insulin sensitivity more potently than bezafibrate. Meanwhile, serum transaminases, creatine phosphokinase and CREA levels were found not altered by ZBH intervention. Mechanism study indicated ZBH promoted the expression of PPARα target genes and SIRT1 mRNA. Hepatic lipogenesis was markedly decreased via down-regulation of lipogenic genes, and fatty acid uptake and oxidation was simultaneously increased in the liver and skeletal muscle via up-regulation of lipolysis genes. Glucose uptake and utilization was also significantly promoted in skeletal muscle. These results suggested that ZBH significantly lowered hyperlipidemia and ameliorated insulin resistance more efficiently than bezafibrate in the hyperlipidemic hamsters primarily by activating of PPARα, and SIRT1 promotion and activation. ZBH thus presents a potential new agent to combat hyperlipidemia.

Synthesis and characterization of ferroelectric liquid crystalline organosiloxanes containing 4-(4-undecanyloxy bi-phenyl-1-carboxyloxy)phenyl (2S,3S)-2-chloro-3-methylvalerate and 4-(4-undecanyloxybenzoyloxy)biphenyl (2S,3S)-2-chloro-3-methylvalerate.

A series of new organosiloxane ferroelectric liquid crystalline (FLC) materials have been synthesized, and their mesomorphic and physical properties have been characterized. Four new disiloxanes and trisiloxanes, containing biphenyl 4-hydroxybenzoate and phenyl 4-hydroxybiphenylcarboxylate as mesogenic units and eleven methylene unit as spacers and (2S,3S)-2-chloro-3-methylvalerate unit as chiral end groups. The molecule, using three phenyl ring as a mesogenic unit, formulates much wider liquid crystalline phase temperature ranges than that of a two phenyl ring unit. The phenyl arrangement differences of mesogenic unit result in the greater differences of the liquid crystal phase formation. The siloxane molecule induction is helpful to the more regular smectic phase formation and smectic phase stabilization, such as chiral SC (SC*) and SB phases. The siloxane molecule is helpful to reduce the phase transition temperature and broaden the liquid crystal temperature range of the SC* phase and, simultaneously, it will not induce chain crystallization phenomenon and dilute the Ps value. The synthesis and characterization of the new FLCs materials, which exhibit a room temperature SC* phase and higher spontaneous polarization are presented.

The development of a new class of inhibitors for betaine-homocysteine S-methyltransferase.

Betaine-homocysteine S-methyltransferase (BHMT) is an important zinc-dependent methyltransferase that uses betaine as the methyl donor for the remethylation of homocysteine to form methionine. In the liver, BHMT performs to half of the homocysteine remethylation. In this study, we systematically investigated the tolerance of the enzyme for modifications at the "homocysteine" part of the previously reported potent inhibitor (R,S)-5-(3-amino-3-carboxy-propylsulfanyl)-pentanoic acid (1). In the new compounds, which are S-alkylated homocysteine derivatives, we replaced the carboxylic group in the "homocysteine" part of inhibitor 1 with different isosteric moieties (tetrazole and oxadiazolone); we suppressed the carboxylic negative charge by amidations; we enhanced acidity by replacing the carboxylate with phosphonic or phosphinic acids; and we introduced pyrrolidine steric constraints. Some of these compounds display high affinity toward human BHMT and may be useful for further pharmacological studies of this enzyme. Although none of the new compounds were more potent inhibitors than the reference inhibitor 1, this study helped to completely define the structural requirements of the active site of BHMT and revealed the remarkable selectivity of the enzyme for homocysteine.

Preparation and double Michael addition reactions of a synthetic equivalent of the Nazarov reagent.

A synthetic equivalent of the Nazarov reagent, the silyl derivative 2, able to undergo base-catalyzed double Michael addition reactions with α,ß-unsaturated carbonyl compounds has been developed. The new reagent satisfactorily reacts with unsaturated indolo[2,3-a]quinolizidine lactams to give pentacyclic yohimbinone-type derivatives.