Synthesis and Validation of TRIFAPYs as a Family of Transfection Agents for Therapeutic Oligonucleotides

Transfection agents play a crucial role in facilitating the uptake of nucleic acids into eukaryotic cells offering potential therapeutic solutions for genetic disorders. However, progress in this field needs the development of improved systems that guarantee efficient transfection. Here, we describe the synthesis of a set of chemical delivery agents (TRIFAPYs) containing alkyl chains of different lengths based on the 1,3,5-tris[(4-alkyloxy-1pyridinio)methyl]benzene tribromide structure. Their delivery properties for therapeutic oligonucleotides were evaluated using PolyPurine Reverse Hoogsteen hairpins (PPRHs) as a silencing tool. The binding of liposomes to PPRHs was evaluated by retardation assays in agarose gels. The complexes had a size of 125 nm as determined by DLS, forming well-defined concentrical vesicles as visualized by Cryo-TEM. The prostate cancer cell line PC-3 was used to study the internalization of the nanoparticles by fluorescence microscopy and flow cytometry. The mechanism of entrance involved in the cellular uptake was mainly by clathrin-mediated endocytosis. Cytotoxicity analyses determined the intrinsic toxicity caused by each TRIFAPY and the effect on cell viability upon transfection of a specific PPRH (HpsPr-C) directed against the antiapoptotic target survivin. TRIFAPYs C12-C18 were selected to expand these studies in the breast cancer cell line SKBR-3 opening the usage of TRIFAPYs for both sexes and, in the hCMEC/D3 cell line, as a model for the blood-brain barrier. The mRNA levels of survivin decreased, while apoptosis levels increased upon the transfection of HpsPr-C with these TRIFAPYs in PC-3 cells. Therefore, TRIFAPYs can be considered novel lipid-based vehicles for the delivery of therapeutic oligonucleotides.

Chiral Aminoalcohol-Derived δ-Lactams Provide Easy Access to Piperidines and Acyclic Five-Carbon Building Blocks Bearing a Tertiary and a Quaternary Stereocenter

A procedure for the synthesis of enantiopure piperidines and acyclic building blocks (5-aminopentanols, O-protected 5-hydroxypentanenitriles) containing a tertiary and a quaternary stereocenter has been developed. Starting from a phenylglycinol- or aminoindanol-derived δ-lactam bearing an alkyl substituent at the α-position of the N,O-acetal carbon, easily accessible by a cyclocondensation reaction, the stereoselective dialkylation at the carbonyl α-position generates the quaternary stereocenter and the subsequent two-step reductive removal of the chiral inductor provides enantiopure 3,3,5-trisubstituted piperidines. Alternatively, the simultaneous reductive opening of the oxazolidine and piperidone rings of the dialkylated lactams followed by reductive or oxidative cleavage of the chiral inductor opens access to chiral 2,2,4-trisubstituted 5-amino-1-pentanols or 2,4,4-trisubstituted 5-hydroxypentanenitriles.

Trioleyl Pyridinium, a Cationic Transfection Agent for the Lipofection of Therapeutic Oligonucleotides into Mammalian Cells

BACKGROUND

One of the most significant limitations that therapeutic oligonucleotides present is the development of specific and efficient delivery vectors for the internalization of nucleic acids into cells. Therefore, there is a need for the development of new transfection agents that ensure a proper and efficient delivery into mammalian cells.

METHODS

We describe the synthesis of 1,3,5-tris[(4-oelyl-1-pyridinio)methyl]benzene tribromide (TROPY) and proceeded to the validation of its binding capacity toward oligonucleotides, the internalization of DNA into the cells, the effect on cell viability, apoptosis, and its capability to transfect plasmid DNA.

RESULTS

The synthesis and chemical characterization of TROPY, which can bind DNA and transfect oligonucleotides into mammalian cells through clathrin and caveolin-mediated endocytosis, are described. Using a PPRH against the antiapoptotic survivin gene as a model, we validated that the complex TROPY-PPRH decreased cell viability in human cancer cells, increased apoptosis, and reduced survivin mRNA and protein levels. TROPY was also able to stably transfect plasmid DNA, as demonstrated by the formation of viable colonies upon the transfection of a dhfr minigene into dhfr-negative cells and the subsequent metabolic selection.

CONCLUSIONS

TROPY is an efficient transfecting agent that allows the delivery of therapeutic oligonucleotides, such as PPRHs and plasmid DNA, inside mammalian cells.

Enantioselective formal synthesis of the marine macrolide (-)-callyspongiolide

A short enantioselective synthesis of the macrocyclic core 19 of callyspongiolide, involving a homocrotylboration of aldehyde 4, a Still-Genari olefination, an esterification with alcohol 17, and a ring-closing metathesis, is reported.

Access to enantiopure 4-substituted 1,5-aminoalcohols from phenylglycinol-derived δ-lactams: synthesis of Haliclona alkaloids

LiNH2BH3-promoted reductive opening of 8-substituted phenylglycinol-derived oxazolopiperidone lactams leads to enantiopure 4-substituted-5-aminopentanols, which are used as starting building blocks in the synthesis of the Haliclona alkaloids haliclorensin C, haliclorensin, and halitulin (formal). The starting lactams are easily accessible by a cyclocondensation reaction of (R)-phenylglycinol with racemic γ-subtituted δ-oxoesters, in a process that involves a dynamic kinetic resolution.

C—H...X(X= O, N or π) interactions in benzyl carbamate

The crystal packing and interaction energy of benzyl carbamate, C8H9NO2, have been analysed in detail by thePIXELmethod. Benzyl carbamate forms layers of hydrogen-bonded molecules, with the layers connected by weaker C—H...π interactions. According to thePIXELanalysis, combinations of C—H...X(X= O, N or π) interactions are comparable in energy with hydrogen bonding. These interactions are necessary for explaining the geometry and the assembly of the layers.

Enantioselective synthesis of alkaloids from phenylglycinol-derived lactams

This review is focused on recent synthetic achievements and ongoing work in our laboratory using phenylglycinol-derived oxazolopiperidone lactams as starting materials for the enantioselective synthesis of piperidine-containing alkaloids: madangamines, 2,5-disubstituted decahydroquinoline and 1-substituted tetrahydroisoquinoline alkaloids, the indole alkaloids 20S- and 20R-dihydrocleavamine and quebrachamine, and indole alkaloids of the uleine and silicine groups.

Enantioselective Synthesis of Alkaloids from Phenylglycinol-Derived Lactams

This review is focused on recent synthetic achievements and ongoing work in our laboratory using phenylglycinol-derived oxazolopiperidone lactams as starting materials for the enantioselective synthesis of piperidine-containing alkaloids: madangamines, 2,5-disubstituted decahydroquinoline and 1-substituted tetrahydroisoquinoline alkaloids, the indole alkaloids 20 S- and 20 R-dihydrocleavamine and quebrachamine, and indole alkaloids of the uleine and silicine groups.

Straightforward methodology for the enantioselective synthesis of benzo[a]- and indolo[2,3-a]quinolizidines

An enantioselective two-step route to substituted benzo[a]- and indolo[2,3-a]quinolizidines has been developed. It consists of (i) a stereoselective cyclocondensation of a racemic or prochiral delta-oxo(di)ester with either (S)-(3,4-dimethoxyphenyl)alaninol or (S)-tryptophanol in a process involving a dynamic kinetic resolution and/or the differentiation of enantiotopic or diastereotopic ester groups, and (ii) a subsequent stereocontrolled cyclization on the aromatic ring taking advantage of the masked N-acyl iminium ion present in the resulting oxazolopiperidone lactams.

Dynamic Kinetic Resolution and Desymmetrization Processes: A Straightforward Methodology for the Enantioselective Synthesis of Piperidines

A straightforward procedure for the synthesis of enantiopure polysubstituted piperidines is reported. It involves the direct generation of chiral non-racemic oxazolo[3,2-a]piperidone lactams that already incorporate carbon substituents on the heterocyclic ring and the subsequent removal of the chiral auxiliary. The key step is a cyclocondensation reaction of (R)-phenylglycinol or other amino alcohols with racemic or prochiral delta-oxo (di)acid derivatives in highly stereoselective processes involving dynamic kinetic resolution and/or desymmetrization of diastereotopic or enantiotopic ester groups.

Biogenetically Inspired Enantioselective Approach to Indolo[2,3-a]- and Benzo[a]quinolizidine Alkaloids from a Synthetic Equivalent of Secologanin

[reaction: see text] Racemic oxodiester 1 undergoes stereoselective cyclocondensation with (S)-tryptophanol, (S)-(3,4-dimethoxyphenyl)alaninol, or the corresponding amino acids, in a process involving a tandem dynamic kinetic resolution/desymmetrization of diastereotopic groups, to give bicyclic lactams, which are cyclized to substituted indolo[2,3-a]- and benzo[a]quinolizidines.

Conjugate Additions to Phenylglycinol-Derived Unsaturated δ-Lactams. Enantioselective Synthesis of Uleine Alkaloids

The stereochemical outcome of the conjugate addition of a variety of stabilized nucleophiles (2-indoleacetic enolates and sulfur-stabilized anions) to the phenylglycinol-derived unsaturated lactams trans-2, cis-2, and its 8-ethyl-substituted analogue 10 is studied. The factors governing the exo or endo facial stereoselectivity are discussed. This methodology provides short synthetic routes to either cis- or trans-3,4-disubstituted enantiopure piperidines as well as efficient routes for the enantioselective construction of the tetracyclic ring system of uleine alkaloids, both in the normal and 20-epi series. The formal total synthesis of several alkaloids of this group is reported.

Enantioselective formal synthesis of uleine alkaloids from phenylglycinol-derived bicyclic lactams

A two-step route for the enantioselective construction of the tetracyclic ring system of uleine alkaloids, involving the stereoselective conjugate addition of an appropriate indole-containing nucleophile to a chiral bicyclic delta-lactam and the subsequent cyclization on the indole 3-position of the resulting 4,5-disubstituted 2-piperidone, has culminated in the formal total synthesis of several alkaloids of this group.

Enantioselective synthesis of cis- and trans-3,5-disubstituted piperidines. Synthesis of 20S- and 20R-dihydrocleavamine

[reaction: see text] Diastereoselective alkylation at the carbonyl alpha-position of chiral nonracemic lactams 2 and 3, the former prepared by cyclocondensation of (R)-phenylglycinol with a racemic gamma-substituted delta-oxoester in a process that involves a dynamic kinetic resolution and the latter by a subsequent equilibration, provides access to enantiopure cis- and trans-3,5-disubstituted piperidines. The usefulness of the approach is illustrated with the synthesis of the alkaloids 20S- and 20R-15,20-dihydrocleavamine.

Enantioselective synthesis of piperidine, indolizidine, and quinolizidine alkaloids from a phenylglycinol-derived delta-lactam

Starting from a common lactam, (3R,8aS)-5-oxo-3-phenyl-2,3,6,7,8,8a-hexahydro-5H-oxazolo[3,2-a]pyridine (1), or its enantiomer, the enantioselective synthesis of 2-alkylpiperidines and cis- and trans-2,6-dialkylpiperidines is reported. The potential of this approach is illustrated by the synthesis of the piperidine alkaloids (R)-coniine, (2R,6S)-dihydropinidine, (2R,6R)-lupetidine, and (2R,6R)-solenopsin A, the indolizidine alkaloids (5R,8aR)-indolizidine 167B and (3R,5S,8aS)-monomorine I, and the nonnatural base (4R,9aS)-4-methylquinolizidine.

Stereodivergent synthesis of enantiopure cis- and trans-3-Ethyl-4-piperidineacetates

[reaction: see text] Starting from a common chiral bicyclic lactam 11, enantiopure trans- or cis-3-ethyl-4-piperidineacetate derivatives are obtained by conjugate addition of an enolate or a cuprate to the unsaturated lactams 12 or 18, respectively.

Dynamic kinetic resolution of racemic gamma-aryl-delta-oxoesters. Enantioselective synthesis of 3-arylpiperidines

Cyclodehydration of racemic gamma-aryl-delta-oxoesters with (R)- or (S)-phenylglycinol stereoselectively affords bicyclic delta-lactams, in a process that involves a dynamic kinetic resolution. Subsequent reduction of these lactams leads to enantiopure 3-arylpiperidines. Starting from racemic aldehyde esters, this short sequence has been applied to the synthesis of (R)-3-phenylpiperidine and the antipsychotic drug (-)-3-PPP (an (S)-3-arylpiperidine), whereas starting from racemic ketone esters enantiopure cis-2-alkyl-3-arylpiperidines are prepared.

Enantioselective synthesis of 2-arylpiperidines from chiral lactams. A concise synthesis of (-)-anabasine

Cyclodehydration of achiral or racemic aryl-delta-oxoacids with (R)-phenylglycinol stereoselectively affords chiral non-racemic bicyclic lactams, from which the enantiodivergent synthesis of (R)- and (S)-2-phenylpiperidine, the diastereodivergent synthesis of cis- and trans-3-ethyl-2-phenylpiperidine, and the enantioselective synthesis of the piperidine alkaloid (-)-anabasine is reported.

Unprecedented oxidation of a phenylglycinol-derived 2-pyridone: enantioselective synthesis of polyhydroxypiperidines

[reaction: see text]. The phenylglycinol-derived 2-pyridone 1 undergoes m-CPBA oxidation steroselectively leading to the chiral nonracemic unsaturated bicyclic hydroxylactam 2, from which the enantioselective synthesis of (3R,5R)-3,4,5-trihydroxypiperidine (16) and the formal synthesis of the azasugar epiisofagomine are described. The enantioselective synthesis of (S)-N-Boc-3-hydroxypiperidine and (3R,4S)-3,4-dihydroxypiperidine is also reported.

Conjugate addition of organocuprates to chiral bicyclic delta-lactams. Enantioselective synthesis of cis-3,4-disubstituted and 3,4,5-trisubstituted piperidines

[reaction: see text] Chiral nonracemic bicyclic lactam 3, easily accessible by cyclodehydration of (R)-phenylglycinol and racemic methyl 4-formylhexanoate, was converted to the unsaturated lactams 5, which undergo the stereoselective conjugate addition of lower order cyanocuprates to ultimately lead to enantiopure cis-3,4-disubstituted and 3,4,5-trisubstituted piperidines.

Synthesis of enantiopure trans-3,4-disubstituted piperidines. An enantiodivergent synthesis of (+)- and (-)-paroxetine

Reaction of (R)-phenylglycinol with methyl 5-oxopentanoate gave either bicyclic lactam cis-1 (the kinetic product) or its isomer trans-1 (under equilibrating conditions) as the major products, which were converted to the corresponding (cis or trans) unsaturated lactams 4 and 5. On treatment with lithium alkyl (or aryl) cyanocuprates, these chiral building blocks undergo conjugate addition to give enantiopure trans-3,4-substituted 2-piperidone derivatives in high yield and stereoselectivity. The synthetic potential of this transformation is illustrated by the synthesis of (+)-femoxetine and the two enantiomers of the known antidepressant paroxetine.