Highly efficient synthesis of β-amino esters via Mannich-type reaction under solvent-free conditions using ZnCl_2 catalyst

β-Amino esters were synthesized via ZnCl2-catalyzed Mannich-type reaction of imines and malonate esters under solvent-free conditions in 6 min. The β-amino ester was converted into the corresponding aspartic acid derivatives.

Free amino group-directed C(sp^(2))-H arylation ofα-amino-β-aryl esters by palladium catalysis

Native amino-directed palladium-catalyzed C(sp^(3))-H activation/functionalization has been developed for modification ofα-amino acids and peptides.Herein a palladium(Ⅱ)-catalyzed C(sp^(2))-H arylation ofα-amino-β-aryl esters has been disclosed,using the native amino as the directing group.A variety of chiralα-amino-β-aryl esters can be functionalized to give the corresponding ortho-substituted mono-and di-arylated products.

Apoptosis of A549 cells by small interfering RNA targeting survivin delivery using poly-β-amino ester/guanidinylated O-carboxymethyl chitosan nanoparticles

Gene-based therapeutics has emerged as a promising approach for human cancer therapy. Among a variety of non-viral vectors, polymer vectors are particularly attractive due to their safety and multivalent groups on their surface. This study focuses on guanidinylated O-carboxymethyl chitosan(GOCMCS) along with poly-β-amino ester(PBAE) for si RNA delivery. Binding efficiency of PBAE/si RNA/GOCMCS nanoparticles were characterized by gel electrophoresis. The si RNA-loaded nanoparticles were found to be stable in the presence of RNase A, serum and BALF respectively. Fine particle fraction(FPF) which was determined by a two-stage impinger(TSI) was 57.8% ± 2.6%. The particle size and zeta potential of the nanoparticles were 153.8 ± 12.54 nm and + 12.2 ± 4.94 m V. In vitro cell transfection studies were carried out with A549 cells. The cellular uptake was significantly increased. When the cells were incubated with si Survivin-loaded nanoparticles, it could induce 26.83% ± 0.59% apoptosis of A549 cells and the gene silencing level of survivin expression in A549 cells were 30.93% ± 2.27%. The results suggested that PBAE/GOCMCS nanoparticle was a very promising gene delivery carrier.

Preparation and Characterization of Poly(β-Amino Ester) Capsules for Slow Release of Bioactive Material

Network structures from poly(β-amino ester) (PAE) were synthesized for applying as drug delivery matrix via a simplified addition polymerization method. It can hold an active organic compound (drug) that has an effect as antitumor activity in order to control its release. PAE was prepared from piperazine and 1,4-butandiol diacrylate with different molar ratios. The active compound was mixed with the prepared polymer while warming for 15 minutes to obtain the capsule product. The resulting polymer structures and the surface morphology of the PAE capsules before and after encapsulation with the active drug were characterized by FT-IR and SEM, respectively. Swelling and degradation behavior of PAE were studied. The characterization showed that the obtained network structure of PAE depends on the molar ratio between the reactants. The optimum ratio of the reactants was found to be 1:1. Therefore, stable and white product as well as good holding capability for drug produced. The SEM studies illustrate good dispersion and holding properties of the drug into the network structure of the prepared polymer. In vitro, the release results of the drug from the PAE capsules indicated that the capsules were able to give sustained release of drug in DMF up to 10 days at 25°C.

Fluorinated amphiphilic Poly(β-Amino ester)nanoparticle for highly efficient and specific delivery of nucleic acids to the Lung capillary endothelium

Endothelial cell dysfunction occurs in a variety of acute and chronic pulmonary diseases including pulmonary hypertension,viral and bacterial pneumonia,bronchopulmonary dysplasia,and congenital lung diseases such as alveolar capillary dysplasia with misalignment of pulmonary veins(ACDMPV).To correct endothelial dysfunction,there is a critical need for the development of nanoparticle systems that can deliver drugs and nucleic acids to endothelial cells with high efficiency and precision.While several nanoparticle delivery systems targeting endothelial cells have been recently developed,none of them are specific to lung endothelial cells without targeting other organs in the body.In the present study,we successfully solved this problem by developing non-toxic poly(β-amino)ester(PBAE)nanoparticles with specific structure design and fluorinated modification for high efficiency and specific delivery of nucleic acids to the pulmonary endothelial cells.After intravenous administration,the PBAE nanoparticles were capable of delivering non-integrating DNA plasmids to lung microvascular endothelial cells but not to other lung cell types.IVIS whole body imaging and flow cytometry demonstrated that DNA plasmid were functional in the lung endothelial cells but not in endothelial cells of other organs.Fluorination of PBAE was required for lung endothelial cell-specific targeting.Hematologic analysis and liver and kidney metabolic panels demonstrated the lack of toxicity in experimental mice.Thus,fluorinated PBAE nanoparticles can be an ideal vehicle for gene therapy targeting lung microvascular endothelium in pulmonary vascular disorders.

Improving gene transfection efficiency of highly branched poly(β-amino ester)s through the in-situ conversion of inactive terminal groups

Highly branched poly(β-amino ester)s(HPAEs)have emerged as a safe and efficient type of non-viral gene delivery vectors.However,the presence of inactive terminal secondary amine groups compromises their gene transfection capability.In this study,HPAEs with similar topological structures and chemical compositions but varying numbers of terminal secondary 4-amino-1-butanol(S4)and secondary/tertiary 3-morpholinopropylamine(MPA)groups were synthesized.The results demonstrate that an increased number of secondary/tertiary MPA groups in-situ significantly enhances the DNA binding capability of HPAEs,leading to the formation of smaller HPAE/DNA polyplexes with higher zeta potential,ultimately resulting in superior gene transfection efficiency in bladder epithelial cells.This study establishes a sim-ple yet effective strategy to maximize the gene transfection potency of HPAEs by converting the inactive terminal groups in-situ without the need for complex modifications to their topological structure and chemical composition.

Lipophilicity determination of N-( benzothiazol-2-yl )-α-amino alkyl phosphonic diesters by RP-HPLC and RP-HPTLC

Using methanol-water mixtures as the mobile phase, the chromatographic retention parameters k' and Rf were determined by reversed-phase high-performance liquid chromatography (RP-HPLC) and reversed-phase high-performance thin-layer chromatography (RP-HPTLC) for N-(benzothiazol-2-yl)-α-amino alkyl phosphoric diesters and the correlation with lipophilicity parameter (Clog P) was established. Log Kw values obtained from RP-HPLC and Rm values obtained from RP-HPTLC can be used to evaluate the lipophilicity of this kind of compounds. Chromatographic method is a good alternative for lipophilicity measurement.

Highly branched poly(β-amino ester)s with narrow molecular weight distribution: Fractionation and gene transfection activity

Highly branched poly(β-amino ester)s(HPAEs) have shown their great promise in gene delivery. However, their broad molecular weight distribution(MWD) poses an additional challenge to the mechanistic understanding of the influence of molecular weight(MW) on their gene transfection activity. Using a stepwise precipitation strategy, HPAEs were fractionated. It is shown that MW has a significant effect on the transfection activity and cytotoxicity of HPAEs. The intermediate MW mediates higher transfection efficiency while maintaining high cell viability. Mechanistic studies show that the intermediate MW confers stronger DNA binding affinity to HPAEs, leading to the formulation of polyplexes with a relatively smaller size and more positive zeta potential. This study not only suggests a simple strategy to fractionate HPAEs with narrow MWD but also provides new insights into understanding the structure-property relationship, which would facilitate the clinical translation of HPAEs in gene therapy.

Efficient gene transfection of suspension cells by highly branched poly(β-amino ester)

Suspension cells play a crucial role in many biological processes. However, compared to adherent cells, it is particularly challenging to introduce exogenous genes into suspension cells to regulate their biological functions with non-viral gene vectors, mainly due to the low cellular uptake and endosomal escape of polyplexes. Herein, to improve the interactions of polyplexes with cellular membranes, we design and synthesize highly branched poly(β-amino ester)(HPAE) via an “A2 + B4 + C2” Michael addition strategy.Results show that branching significantly increases DNA condensation of HPAE, cellular uptake and endosomal escape of HPAE/DNA polyplexes. In mast cells(MCs), HPAE exhibits up to 80-fold higher gene transfection efficiency compared to the corresponding linear poly(β-amino ester)(LPAE) and the leading commercial gene transfection reagents PEI25k, jetPEI, and Lipofectamine 3000, without causing obvious cytotoxicity. Our study establishes a reliable non-viral platform for efficient gene transfection of suspension cells.

Formation of Chiral a-Monofluorinated-.8-amino Esters through Organocatalytic Asymmetric Reduction of a-Fluoro-j3-enamino Esters by Trichlorosilane

A concise method was developed to prepare chiral a-monofluorinated-β-amino esters through N-sulfinyl urea catalyzed asymmetric hydrosilylation of a-fluoro-β-enamino esters, which affords high yields, good to high di- astereoselectivities （up to〉99/1）, and moderate to good enantioselectivities （up to 83% ee）.

SmI_2-promoted imino-Reformatsky reaction for facile synthesis of enantioenriched β-amino acid esters

A facile and efficient method for the stereoselective synthesis of β-amino acid esters via SmI2-promoted imino-Reformatsky reaction is described.Asymmetric addition of tert-butyl bromoacetate to N-tert-butanesulfinyl aldimines afforded β-amino acid esters in moderate to high yields with excellent diastereoselectivities.The synthetic utilities of the tert-butyl β-amino acid esters were expanded by the preparation of β-lactams and 3-aminoindan-1-ones derivatives.

One-pot synthesis of novel pyrrolo-1,4-benzoxazines via a three- component reaction of 2-amino phenols, acetylenic esters and nitrostyrene derivatives

A simple and efficient synthetic protocol has been developed using a one-pot, three-component reaction involving 2-amino phenols, dialkyl acetylene dicarboxylates and nitrostyrene derivatives. Utilizing this protocol, a variety of novel pyrrolo-1,4-benzoxazine derivatives were synthesized in excellent yields.

pH-Responsive supramolecular micelle based on host-guest interaction of poly(β-amino ester) derivatives and adamantyl-terminated poly(ethylene glycol) for cancer inhibition

Supramolecular structures have received growing attention and been widely applied in many fields.Herein, we synthesized hydrophobic β-cyclodextrin-contained poly(β-amino ester)(PAE-β-CD) and hydrophilic adamantyl-terminated poly(ethylene glycol)(PEG-AD) to form a supramolecular micelle via the host-guest interaction. The micelle displayed pH responsive structure change due to the transform of hydrophobic PAE core to hydrophilic form in weakly acid condition. After the anticancer drug curcumin(Cur) was loaded into the micelle, the drug release behavior of the Cur-loaded micelle was studied, and it turned out that the Cur-loaded supramolecular micelle could effectively unload the drug at pH 5.5.Furthermore, the antitumor efficiency of the Cur-loaded micelle was also examined both in vitro and in vivo, indicating considerable inhibition ratio as high as 62.14% against mouse sarcoma 180.

Enantioselective trapping of oxonium ylide intermediates by N-benzhydryl-α-imino ester：Synthesis of β-tetrasubstituted α-amino acids

A synergistic rhodium（Ⅱ）/phosphoric acid catalyzed three component reaction of 3-diazooxindoles,alcohols and N-benzhydryl-α-imino ester is developed for the efficient construction of chiral β-alkoxy C-β-tetrasubstituted α-amino acid derivatives in good yields and with excellent diastereoselectivities and high enantioselectivities.The synthetic application of the resulting products was illustrated by reducing with Pd/C under H_2 atmosphere followed reacting with CSCl_2 at room temperature to rapid afford 3-spirocyclic oxindole in a good yield with a chirality retainment.The three-component reaction is proposed to proceed through an electrophilic trapping of the oxonium ylides by N-benzhydryl-α-imino ester.

Macrophage-targeting gene silencing orchestrates myocardial microenvironment remodeling toward the anti-inflammatory treatment of ischemia-reperfusion (IR) injury

Ischemia-reperfusion (IR) injury represents a major cause of myocardial dysfunction after infarction and thrombolytic therapy, and it is closely related to the free radical explosion and overwhelming inflammatory responses. Herein, macrophage-targeting nanocomplexes (NCs) are developed to mediate efficient co-delivery of siRNA against MOF (siMOF) and microRNA-21 (miR21) into myocardial macrophages, cooperatively orches-trating the myocardial microenvironment against IR injury. Bioreducible, branched poly(β-amino ester) (BPAE-SS) is designed to co-condense siMOF and miR21 into NCs in a multivalency-reinforced approach, and they are surface-decorated with carboxylated mannan (Man-COOH) to shield the positive surface charges and enhance the serum stability. The final MBSsm NCs are efficiently internalized by myocardial macrophages after systemic administration, wherein BPAE-SS is degraded into small segments by intracellular glutathione to promote the siMOF/miR21 release, finally provoking efficient gene silencing. Thus, cardiomyocyte protection and macro-phage modulation are realized via the combined effects of ROS scavenging, inflammation inhibition, and autophagy attenuation, which ameliorates the myocardial microenvironment and restores the cardiac function via positive cellular crosstalk. This study renders promising solutions to address the multiple systemic barriers against in vivo nucleic acid delivery, and it also offers new options for IR injury by manipulating multiple reciprocal bio-reactions.

Co-delivery of luteolin and TGF-β1 plasmids with ROS-responsive virus-inspired nanoparticles for microenvironment regulation and chemo-gene therapy of intervertebral disc degeneration

Intervertebral disc degeneration(IDD)is closely related to inflammation and imbalance of synthesis/catabolism of extracellular matrix(ECM)in intervertebral disc(IVD).Considering this,luteolin(LUT),a kind of natural flavonoid with good anti-inflammatory effect and TGF-β1(a gene that promotes the regeneration of ECM)plasmid was co-loaded and co-delivered to nucleus pulposus cells(NPCs).Reactive oxygen species(ROS)responsive cationic copolymer,poly(β-amino ester)-poly(ε-caprolactone)(PBC),with high plasmid DNA(pDNA)compression affinity was synthesized.It can self-assemble into nano-sized polyplexes(pDNA@PBC)with virus-inspired structure and function through which it can transfect pDNA into NPCs with very high efficiency and negligible cytotoxicity.LUT was encapsulated in the hydrophobic core of pDNA@PBC.The co-delivery system,LUT-pTGFβ1@PBC,could enhance the cellular uptake of NPCs and manifest excellent sustained drug release in IVD.Real time quantitative polymerase chain reaction(RT-qPCR)and Western blot experiments reveal that the co-delivery system could inhibit inflammation in NPCs and restore the balance of anabolism and catabolism in vitro by activating TGF/SMAD3 and inhibiting NFkB/p65.Moreover,LUT-pTGF-β1@PBC retards IDD in vivo as detected by radiological and histological methods with good biosafety in rats.LUT-pTGF-β1@PBC may be a promising option for the treatment of IDD.