Kinetic Resolution of 2-Aryl-4-methylenepiperidines toward Enantioenriched Functionalizable Piperidine Fragments.

The base n-BuLi with sparteine allows a kinetic resolution of N-Boc-2-aryl-4-methylenepiperidines. The 2,2-disubstituted products and recovered starting materials were isolated with high enantiomeric ratios. From VT-NMR spectroscopy and DFT studies, the rate of rotation of the N-Boc group is fast. Lithiation and trapping of the enantioenriched starting materials gave 2,2-disubstituted piperidines with retention of stereochemistry. Functionalization of the 4-methylene group led to a variety of 2,4-disubstituted piperidines without loss of enantiopurity that could be useful building blocks for drug discovery.

New arylsparteine derivatives as positive inotropic drugs.

Positive inotropic agents are fundamental in the treatment of heart failure; however, their arrhythmogenic liability and the increased myocardial oxygen demand strongly limit their therapeutic utility. Pursuing our study on cardiovascular activities of lupin alkaloid derivatives, several 2-(4-substituted-phenyl)-2-dehydrosparteines and 2-(4-substituted-phenyl)sparteines were prepared and tested for inotropic and chronotropic activities on isolated guinea pig atria. Four compounds (6b, 6e, 7b, and 7f) exhibited significant inotropism that, at the higher concentrations, was followed by negative inotropism or toxicity. Compound 7e (2-(4-tolyl)sparteine) exhibited a steep dose-depending inotropic activity up to the highest concentration tested (300 µM) with an Emax of 116.5 ± 3.4% of basal force, proving less potent but much more active in comparison to the highest concentrations tested of digoxin and milrinone having Emax of 87.5 ± 3.1% and 52.2 ± 1.1%, respectively. Finally, docking studies suggested that the relevant sparteine derivatives could target the sigma-1 receptor, whose involvement in cardiac activity is well documented.

In Vivo and In Vitro Activities and ADME-Tox Profile of a Quinolizidine-Modified 4-Aminoquinoline: A Potent Anti-P. falciparum and Anti-P. vivax Blood-Stage Antimalarial.

Natural products are a prolific source for the identification of new biologically active compounds. In the present work, we studied the in vitro and in vivo antimalarial efficacy and ADME-Tox profile of a molecular hybrid (AM1) between 4-aminoquinoline and a quinolizidine moiety derived from lupinine (Lupinus luteus). The aim was to find a compound endowed with the target product profile-1 (TCP-1: molecules that clear asexual blood-stage parasitaemia), proposed by the Medicine for Malaria Venture to accomplish the goal of malaria elimination/eradication. AM1 displayed a very attractive profile in terms of both in vitro and in vivo activity. By using standard in vitro antimalarial assays, AM1 showed low nanomolar inhibitory activity against chloroquine-sensitive and resistant P. falciparum strains (range IC50 16-53 nM), matched with a high potency against P. vivax field isolates (Mean IC50 29 nM). Low toxicity and additivity with artemisinin derivatives were also demonstrated in vitro. High in vivo oral efficacy was observed in both P.berghei and P. yoelii mouse models with IC50 values comparable or better than those of chloroquine. The metabolic stability in different species and the pharmacokinetic profile in the mouse model makes AM1 a compound worth further investigation as a potential novel schizonticidal agent.

Recent advances in asymmetric synthesis of Ð -stereogenic phosphorus compounds.

This chapter points out significant advances in the asymmetric synthesis of P-chiral organophosphorus compounds with many applications in stereoselective synthesis and in asymmetric catalysis, making reference to updated literature findings as well as the author's original research. Asymmetric addition and cycloaddition reactions, oxidation, including metal catalyzed and non-metal biocatalytic methods are described, in addition to synthetic approaches via nucleophilic substitution of appropriately substituted precursors. Use of chiral organophosphorus compounds in some asymmetric transformations such as hydrogenation and alkyl/arylation reactions is also discussed.

The Use of (-)-Sparteine/Organolithium Reagents for the Enantioselective Lithiation of 7,8-Dipropyltetrathia[7]helicene: Single and Double Kinetic Resolution Procedures.

The effect of organolithium reagent (RLi: R=nBu, iPr, sBu, tBu), solvent (diethyl ether, diethyl ether/THF and MTBE), and stoichiometry on the (-)-sparteine-mediated silylation of 7,8-dipropyltetrathia[7]helicene shows that, unusually, substantially more than 0.5 equivalent of RLi (R=iPr, sBu, tBu) and a large excess of (-)-sparteine (R=nBu, sBu) is often needed to achieve substantial conversions and good ee values. With nBuLi, however, just one equivalent of the organolithium reagent is sufficient to obtain high conversions. Our best results were obtained using the convenient tBuLi/(-)-sparteine adduct with which the need for a high (-)-sparteine/RLi ratio can be avoided. Single- and double-kinetic resolution (KR) procedures give enantiopure samples of 2-trimethylsilyl- and 2,13-di(trimethylsilyl)-7,8-dipropyltetrathia[7]helicene and two-step double-KR combining (-)-sparteine/sBuLi and chiral formamides affords the synthetically valuable 2-formyl-7,8-dipropyltetrathia[7]helicene. This is the first use of (-)-sparteine for the enantioselective lithiation of helicenes and the first report of tBuLi outperforming sBuLi in a (-)-sparteine-mediated procedure.

Highly enantioselective (-)-sparteine-mediated lateral metalation-functionalization of remote silyl protected ortho-ethyl N,N-dialkyl aryl O-carbamates.

We report the enantioselective, lateral deprotonation of ortho-protected or functionalized tertiary N,N-dialkyl aryl O-carbamates 5-7 (Scheme 2 ) and meta-protected carbamates 14, 15, and 20 (Schemes 5 and 7 ) by s-BuLi/(-)-sparteine and subsequent quench with a variety of electrophiles to give products 11-13 and 16, 17, and 21 in yields up to 96% and enantiomeric ratios up to 99:1. The influence of organolithium reagents, ratio of organolithium/(-)-sparteine pair versus N,N-dialkyl aryl O-carbamate starting materials, temperature, solvents, electrophiles, substituents located ortho or meta to the O-carbamate moiety, and O-carbamate N-substituents was investigated. The identical absolute configuration of the stereogenic center of the major enantiomers of the products, as established by single-crystal X-ray analysis for substrates (S)-11c, (S)-19, and (S)-21a, provides evidence for a consistent stereochemical course in the enantioselective deprotonation. Mechanistic investigations, including an estimate of the configurational stability of the benzyllithium species 9 (starting from 12e; Scheme 8 ) and 23 (starting from 17e; Scheme 9 ), both derived by tin-lithium exchange, and 24 (starting from 20; Scheme 9 ) are reported. The experimental results, together with semiempirical molecular orbital calculations (PM3/SMD), are consistent with a process in which enantioinduction occurs in the deprotonation step (Scheme 11 ).

Enantioselective carbolithiation of S-alkenyl-N-aryl thiocarbamates: kinetic and thermodynamic control.

The addition of n-butyllithium to alkenylthiocarbamates in the presence of (-)-sparteine or the (+)-sparteine surrogate leads to asymmetric carbolithiation, and returns enantiomerically enriched thiocarbamate derivatives of secondary thiols. In THF, with the (+)-sparteine surrogate, in situ aryl migration leads to an enantiomerically enriched tertiary thiol derivative. Remarkably, the two pseudoenantiomeric chiral ligands do not always give enantiomeric products, probably as a result of a complex interplay of kinetic and thermodynamic control. In situ IR and NMR studies of a stable, hindered lithiated thiocarbamate demonstrated its chemical and configurational stability over a period of hours at 0 °C.

Assessing the genotoxicities of sparteine and compounds isolated from Lupinus mexicanus and L. montanus seeds by using comet assay.

The genus Lupinus is widely distributed. Its seeds are used for animal and human food, and Lupinus possesses pharmacological potential because of its high content of quinolizidine alkaloids and flavonoids; however, there is little available information about its genotoxicity. We used the comet assay and staminal nuclei of Tradescantia (clone 4430) to evaluate the in vitro genotoxicity of 4 concentrations (0.01, 0.1, 0.5, and 1.0 mM) of alkaloid extracts of Lupinus mexicanus and Lupinus montanus, flavonoids of L. mexicanus, and commercial sparteine; nitrosodiethylamine was used as a positive control and untreated nuclei were used as a negative control. All concentrations of L. mexicanus and L. montanus showed significant genotoxic activity (P ≤ 0.05). A similar behavior was observed for flavonoid extracts of L. montanus except the 1.0 mM concentration. Sparteine showed genotoxic activity only at 0.5 mM. The order of genotoxicity of the compounds studied was as follows: L. mexicanus > L. montanus > flavonoids of L. montanus > sparteine. There is evident genotoxic activity in the compounds that were studied, particularly at lower concentrations (0.01 and 0.1 mM). Given the limited information about the genotoxicity of the compounds of L. mexicanus and L. montanus, further studies are necessary.

Synthesis of 1-substituted tetrahydroisoquinolines by lithiation and electrophilic quenching guided by in situ IR and NMR spectroscopy and application to the synthesis of salsolidine, carnegine and laudanosine.

The lithiation of N-tert-butoxycarbonyl (N-Boc)-1,2,3,4-tetrahydroisoquinoline was optimized by in situ IR (ReactIR) spectroscopy. Optimum conditions were found by using n-butyllithium in THF at -50 °C for less than 5 min. The intermediate organolithium was quenched with electrophiles to give 1-substituted 1,2,3,4-tetrahydroisoquinolines. Monitoring the lithiation by IR or NMR spectroscopy showed that one rotamer reacts quickly and the barrier to rotation of the Boc group was determined by variable-temperature NMR spectroscopy and found to be about 60.8 kJ mol(-1), equating to a half-life for rotation of approximately 30 s at -50 °C. The use of (-)-sparteine as a ligand led to low levels of enantioselectivity after electrophilic quenching and the "poor man's Hoffmann test" indicated that the organolithium was configurationally unstable. The chemistry was applied to N-Boc-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline and led to the efficient synthesis of the racemic alkaloids salsolidine, carnegine, norlaudanosine and laudanosine.

Total synthesis of hygrolines and pseudohygrolines.

A concise two-step synthesis of all four diastereoisomeric hygrolines ((-)-hygroline (1), (+)-hygroline (2), (-)-pseudohygroline (3), (+)-pseudohygroline (4)) has been developed based on the (-)-sparteine (5)- or (+)-sparteine surrogate 11-mediated enantioselective lithiation of N-Boc pyrrolidine (6), followed by reaction of the chiral anion with (S)- or (R)-propylene oxide. Reduction of the resulting N-Boc amino alcohols furnished hygrolines and pseudohygrolines in 30% to 56% overall yields with dr's > 95:5.

Rotational spectra of bicyclic decanes: the trans conformation of (-)-lupinine.

The conformational and structural properties of the bicyclic quinolizidine alkaloid (-)-lupinine have been investigated in a supersonic jet expansion using microwave spectroscopy. The rotational spectrum is consistent with a single dominant trans conformation within a double-chair skeleton, which is stabilized by more than 10.4 kJ mol(-1) with respect to other conformations. In the isolated conditions of the jet, the hydroxy methyl side chain of the molecule locks in to form an intramolecular O-H···N hydrogen bond to the electron lone pair at the nitrogen atom. Accurate rotational constants, centrifugal distortion corrections, and (14)N nuclear quadrupole coupling parameters are reported and compared to ab initio (MP2) and DFT (M06-2X) calculations. The stability of lupinine is further compared computationally with epilupinine and decaline in order to gauge the influence of intramolecular hydrogen bonding, absent in these molecules.

Asymmetric synthesis of trans-2,3-disubstituted indoline derivatives.

A novel method for asymmetric synthesis of trans-2,3-disubstituted indolines has been developed. The strategy involves the (-)-sparteine-mediated electrophilic substitution of 2-benzyl N-pivaloylaniline with aromatic or α,ß-unsaturated aldehydes and subsequent intramolecular nucleophilic substitution. The simple protocol for two-step process can produce highly enantioenriched indolines 3a-o up to 98:2 er.

Synthesis and comparison of antiplasmodial activity of (+), (-) and racemic 7-chloro-4-(N-lupinyl)aminoquinoline.

Recently the N-(-)-lupinyl-derivative of 7-chloro-4-aminoquinoline ((-)-AM-1; 7-chloro-4-{N-[(1S,9aR)(octahydro-2H-quinolizin-1-yl)methyl]amino}quinoline) showed potent in vitro and in vivo activity against both Chloroquine susceptible and resistant strains of Plasmodium falciparum. However, (-)-AM-1 is synthesized starting from (-)-lupinine, an expensive alkaloid isolated from Lupinus luteus whose worldwide production is not sufficient, at present, for large market purposes. To overcome this issue, the corresponding racemic compound, derived from synthetic (±)-lupinine was considered a cheaper alternative for the development of a novel antimalarial agent. Therefore, the racemic and the 7-chloro-4-(N-(+)-lupinyl)aminoquinoline ((±)-AM-1; (+)-AM-1) were synthesized and their in vitro antimalarial activity and cytotoxicity compared with those of (-)-AM-1. The (+)-lupinine required for the synthesis of (+)-AM-1 was obtained through a not previously described lipase catalyzed kinetic resolution of (±)-lupinine. In terms of antimalarial activity, (±)-AM1 and (+)-AM1 demonstrated very good activity in vitro against both CQ-R and CQ-S strains of P. falciparum (range IC(50) 16-35 nM), and low toxicity against human normal cell lines (therapeutic index >1000), comparable with that of (-)-AM1. These results confirm that the racemate (±)-AM1 could be considered as a potential antimalarial agent, ensuring a decrease of costs of synthesis compared to (-)-AM1.

[Reversible lupininin inhibitors of cholinesterases of mammalian blood and of optical ganglia of individuals of the commander squid Berryteuthis magister from different zones of species areal].

Arylsulfoesters and carbonic lupinin esters are studied for the first time as reversible inhibitors of mammalian blood cholinesterases. Studied in detail is sensitivity of cholinesterases to mono- and bislupinin inhibitors in Commander squid individuals from different habitation zones.

[Derivatives of lupinin and epilupinin as ligands of various cholinesterases].

Literature data have been summarized on interaction of cholinesterases of some mammals and arthropods with a group of isomer derivatives of alkaloid lupini and its epimer epilupinin. As substrates of cholinesterases of several mammals there are studied 8 acetates containing in their molecules the chinolysidin bicycle with different structure of N-alkyl radical, which showed certain elements of specificity of action. For 2 isomer esters that are derivatives of the protonated base of the lupinin and epilupinin structures, differences in their substrate characteristics were revealed. The polyenzyme analysis if anticholinesterase efficiency was performed for 30 organophosphorus inhibitors that are dialkoxyphosphorus derivatives of lupinin and epilupinin; as a result, quite a few peculiarities of their action depending on their structure were revealed. Several tested compounds turned out to act as specific inhibitors of cholinesterases of some mammals and arthropods.

Reaction of O2 with [(-)-sparteine]Pd(H)Cl: evidence for an intramolecular [H-L]+ "reductive elimination" pathway.

(Sp)PdCl(2) [Sp = (-)-sparteine] catalyzes a number of different aerobic oxidation reactions, and reaction of O(2) with a Pd(II)-hydride intermediate, (Sp)Pd(H)Cl (1), is a key step in the proposed catalytic mechanism. Previous computational studies suggest that O(2) inserts into the Pd(II)-H bond, initiated by abstraction of the hydrogen atom by O(2). Experimental and computational results obtained in the present study challenge this conclusion. Oxygenation of in-situ-generated (Sp)Pd(H)Cl exhibits a zero-order dependence on [O(2)]. This result is inconsistent with a bimolecular H-atom-abstraction pathway, and DFT computational studies identify a novel "reductive elimination" mechanism, in which the chelating nitrogen ligand undergoes intramolecular deprotonation of the Pd(II)-hydride. The relevance of this mechanism to other Pd(II) oxidation catalysts with chelating nitrogen ligands is evaluated.

Enantioselective, palladium-catalyzed α-arylation of N-Boc pyrrolidine: in situ react IR spectroscopic monitoring, scope, and synthetic applications.

A comprehensive study of the enantioselective Pd-catalyzed α-arylation of N-Boc pyrrolidine has been carried out. The protocol involves deprotonation of N-Boc pyrrolidine using s-BuLi/(-)-sparteine in TBME or Et(2)O at -78 °C, transmetalation with ZnCl(2) and Negishi coupling using Pd(OAc)(2), t-Bu(3)P-HBF(4) and the aryl bromide. This paper reports several new features including in situ React IR spectroscopic monitoring of the process; use of (-)-sparteine and the (+)-sparteine surrogate to access products with opposite configuration; development of a catalytic asymmetric lithiation-Negishi coupling reaction; extension to a wide range of heteroaromatic bromides; total synthesis of (R)-crispine A, (S)-nicotine and (S)-SIB-1508Y via short synthetic routes; and examples of α-vinylation of N-Boc pyrrolidine using vinyl bromides exemplified by the total synthesis of naturally occurring (+)-maackiamine (thus establishing its configuration as (R)). In this way, the full scope and limitations of the methodology are delineated.

Total synthesis of (+)-epilupinine via an intramolecular nitrile oxide-alkene cycloaddition.

Total synthesis of (+)-epilupinine was accomplished in nine steps and in 48% overall yield, in which INOC was used as the key step for the construction of the quinolizidine skeleton. We found that it was an extremely difficult task to prepare the key intermediates (R)-N-(3-nitropropyl)-2-vinylpiperidine or (R)-(2-vinylpiperid-1-yl)propanal by routine methods. Thus, by using Fukuyama's oxime synthesis, a general method was developed for highly efficient conversion of 3-(N,N-dialkylamino)propanols into 3-(N,N-dialkylamino)propanal oximes without using the corresponding aldehydes.

Synthesis of the azaphilones (+)-sclerotiorin and (+)-8-O-methylsclerotiorinamine utilizing (+)-sparteine surrogates in copper-mediated oxidative dearomatization.

Enantioselective syntheses of the azaphilone natural products (+)-sclerotiorin and (+)-8-O-methylsclerotiorinamine that possess the natural R-configuration at the quaternary center are reported. The syntheses were accomplished using copper-mediated asymmetric dearomatization employing bis-µ-oxo copper complexes prepared from readily available (+)-sparteine surrogates. Of note, site-selective O-methylation of a vinylogous pyridone was used to access the isoquinolin-6(7H)-one core of (+)-8-O-methylsclerotiorinamine.

Development and application of a method to investigate drug-metabolizing enzyme inhibitors using sparteine for probe of cytochrome P450 2D6 and tris(2,2'-bipyridine)ruthenium(II)-electrogenerated chemiluminescence detection.

We studied the detection of drug-metabolizing enzyme inhibitiors using column-switching high performance liquid chromatography with tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)(3)(2+))-electrogenerated chemiluminescence detection. This can be applied to evaluate the genetic diversity concerning the ability of cytochrome P450 (CYP) 2D6 to metabolize drug in vitro. We demonstrated the ability of CYP2D6 to enable us to examine drugs metabolizing enzyme inhibition with high performance and sensitivity. This method can be applied to investigate metabolite inhibitors of CYP2D6 in vitro and in vivo. Thus, Metixene was found to be a potential CYP2D6 inhibitor.