Kai Bao

A novel type of N-formylation and related reactions of amines via cyanides and esters as formylating agents.

A novel N-formylation and related reactions proceed from cyanides promoted by esters.

Immunomodulatory Effects of Erythromycin and its Derivatives on Human T-Lymphocyte In Vitro

To elucidate the immunomodulatory mechanisms of macrolides, we investigated here the effects of erythromycin (EM) and its derivatives, 1 and 2, which show no antibacterial activity, on the proliferation and the activation of the transcription factor nuclear factor-κB (NF-κB) in Jurkat T cells. MTT assay revealed that EM, 1 and 2 could inhibit T lymphocyte proliferation markedly. Flow cytometry and TUNEL analysis showed EM (30 μg/mL–100 μg/mL) and 1 (3 μg/mL–30 μg/mL) could induce T lymphocyte apoptosis, 2 (3 μg/mL–30 μg/mL) induced a cell cycle arrest in G2/M. RT-PCR and Western blotting analysis conformed that EM and its two derivatives could inhibit the expressions of NF-κB mRNA and protein. Taken together, these data suggest EM and its derivatives, 1 and 2, have immunomodulatory effect, presumably via an interaction with the NF-κB expression, inhibiting the proliferation of T lymphocyte, implicating an approach for the development of new drugs for treating inflammatory diseases.

In vitro effects of erythromycin on RANKL and nuclear factor-kappa B by human TNF-α stimulated Jurkat cells

The receptor activator of NF-kappaB ligand (RANKL) and its signal downstream nuclear factor-kappaB (NF-kappaB) are critical regulators for immune responses as well as bone remodeling. The present study aimed to examine the effects of erythromycin (EM) on the activation of RANKL, correlation with NF-kappaB expression, proliferation and apoptosis of human Jurkat T cells. Jurkat T cells were pretreated with 100 pmol/l tumor necrosis factor-alpha (TNF-alpha) for 1 h followed by various concentrations of EM for 24 h. The mRNA expressions of RANKL and NF-kappaB were examined by RT-PCR. The protein expression of NF-kappaB was analyzed by Western blot. The protein level of RANKL was examined by flow cytometry, immunofluorescence microscopy and Western blot analyses. We also examined proliferation of Jurkat T cells by MTT assay, apoptosis by flow cytometry analysis after staining with PI and morphological observation after AO/EB staining. The results showed that EM inhibited TNF-alpha-induced expressions of RANKL and NF-kappaB at both mRNA and protein levels in a concentration-dependent manner. The expression of RANKL was correlated with the expression of NF-kappaB. Moreover, EM influenced the proliferation and apoptosis of human Jurkat T cells. These data suggest that EM acts as an anti-inflammatory agent not only to interact with the expression of NF-kappaB and the proliferation of human Jurkat T cells, but also to reduce the level of RANKL.

Ultrasound-promoted two-step synthesis of 3-arylselenylindoles and 3-arylthioindoles as novel combretastatin A-4 analogues

A series of 3-(3′-hydroxy-4′-methoxyphenyl)selenyl-5,6,7-trimethoxy-1H-indoles and 3-(3′-hydroxy-4′-methoxyphenyl)thio-5,6,7-trimethoxy-1H-indoles were obtained as a new class of combretastatin A-4 (CA-4) analogues via a convenient ultrasound (US)-assisted two-step process involving 3-selenenylation/sulfenylation followed by O-deallylation. With the assistance of US irradiation, both the reaction rates and yields of selenenylation, sulfenylation and O-deallylation could be significantly improved. A comparison of the reaction rates of O-deallylation and ester reduction demonstrated that O-deallylation was more sensitive to US irradiation. Finally, these products were evaluated for their antiproliferative activities, and most of them showed moderate to potent activities against three human cancer cell lines in vitro.

Synthesis of (±) homoisoflavanone and corresponding homoisoflavane

The total synthesis of racemic 3-(4′-methoxybenzyl)-7,8-methylenedioxy-chroman-4-one, a homoisoflavanone with antimycobacterial activity isolated recently from Chlorophytum inornatum, was described. During this research, the first approach for the conversion of homoisoflavonoids into homoisoflavanes was also developed.

Activated carbon for aerobic oxidation: Benign approach toward 2-benzoylbenzimidazoles and 2-benzoylbenzoxazoles synthesis.

A general strategy involving a novel and highly efficient aerobic benzylic oxidation promoted by cheap, reusable activated carbon in water is developed. Application of this method has been demonstrated in the benign synthesis of bioactive 2-benzoylbenzimidazoles and 2-benzoylbenzoxazoles derivatives. Furthermore, the activated carbon catalyst could be recovered and reused at least three times without significantly losing its activity. Preliminary research suggests that the oxidation mechanism may involve intermediate hydroperoxidation and that a portion of the final carbonyl product is obtained through a secondary benzylic alcohol intermediate. Finally, theoretical calculations reveal that the oxidation yield is closely associated with the electric density at the benzylic position of the substrate.

Design, synthesis and structure-activity relationship of 3,6-diaryl-7 H -[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines as novel tubulin inhibitors

A novel series of 3,6-diaryl-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines were designed, synthesized and biologically evaluated as vinylogous CA-4 analogues, which involved a rigid [1,2,4]triazolo[3,4-b][1,3,4]thiadiazine scaffold to fix the configuration of (Z,E)-butadiene linker of A-ring and B-ring. Among these rigidly vinylogous CA-4 analogues, compounds 4d, 5b, 5i, 6c, 6e, 6g, 6i and 6k showed excellent antiproliferative activities against SGC-7901, A549 and HT-1080 cell lines with IC50 values at the nanomolar level. Compound 6i showed the most highly active antiproliferative activity against the three human cancer cell lines with an IC50 values of 0.011–0.015 µM, which are comparable to those of CA-4 (IC50 = 0.009–0.013 µM). Interestingly, SAR studies revealed that 3,4-methylenedioxyphenyl, 3,4-dimethoxyphenyl, 3-methoxyphenyl and 4-methoxyphenyl could replace the classic 3,4,5-trimethoxyphenyl in CA-4 structure and keep antiproliferative activity in this series of designed compounds. Tubulin polymerization experiments showed that 6i could effectively inhibit tubulin polymerization, which was corresponded with CA-4, and immunostaining experiments suggested that 6i significantly disrupted microtubule/tubulin dynamics. Furthermore, 6i potently induced cell cycle arrest at G2/M phase in SGC-7901 cells. Competitive binding assays and docking studies suggested that compound 6i binds to the tubulin perfectly at the colchicine binding site. Taken together, these results revealed that 6i may become a promising lead compound for new anticancer drugs discovery.

Synthesis and antiproliferative activity of 2-aryl-4-(3,4,5-trimethoxybenzoyl)-1,2,3-triazol derivatives as microtubule-destabilizing agents

A series of 2-aryl-4-(3,4,5-trimethoxybenzoyl)-1,2,3-triazols were designed as analogs of substituted methoxybenzoyl-aryl-thiazole (SMART) under the consideration of geometric features. The target compounds were synthesized via concise and efficient processes including microwave-assisted cyclization, and were evaluated for their antiproliferative activity against three human cancer cell lines. Most compounds exhibited moderate antiproliferative activity with IC50 values in the micromolar to sub-micromolar range. Tubulin polymerization and immunofluorescence studies demonstrated that (Z)-9a was a potent microtubule-destabilizing agent and disrupted the polymerization dynamics. Moreover, (Z)-9a significantly induced accumulation of cells in the G2/M phase and caused microtubule destabilization. Molecular modeling studies showed that (Z)-9a probably binds to the colchicine site of tubulin.

Synthesis of Ring-Contracted Erythromycin A Derivatives via Microwave-Assisted Intramolecular Transesterification

The synthesis of ring-contracted derivatives of erythromycin A via intramolecular transesterification under microwave irradiation of 8,9-anhydroerythromycin A 6,9-hemiketal and its derivatives is described. It was found that microwave irradiation could significantly improve the yields and shorten the reaction times under either solvent-containing (method A) or solvent-free (method B) conditions.

Synthesis and bioevaluation of N,4-diaryl-1,3-thiazole-2-amines as tubulin inhibitors with potent antiproliferative activity

A series of N,4-diaryl-1,3-thiazole-2-amines containing three aromatic rings with an amino linker were designed and synthesized as tubulin inhibitors and evaluated for their antiproliferative activity in three human cancer cell lines. Most of the target compounds displayed moderate antiproliferative activity, and N-(2,4-dimethoxyphenyl)-4-(4-methoxyphenyl)-1,3-thiazol-2-amine (10s) was determined to be the most potent compound. Tubulin polymerization and immunostaining experiments revealed that 10s potently inhibited tubulin polymerization and disrupted tubulin microtubule dynamics in a manner similar to CA-4. Moreover, 10s effectively induced SGC-7901 cell cycle arrest at the G2/M phase in both concentration- and time-dependent manners. The molecular docking results revealed that 10s could bind to the colchicine binding site of tubulin.