Boc-L-proline

Trans-β-lactam isomers have garnered much attention as anti-cancer microtubule targeting agents. Currently available synthetic methods are available for the preparation of enantiopure β-lactams and favour isomeric cis/trans β-lactam mixtures. Indirect chiral resolution offers the opportunity for isolation of exclusively enantiopure trans-β-lactams. In this study, liquid chromatography chiral resolution of β-lactams derivatized as diastereomer mixtures with a panel of N-protected amino acids is explored, where N-(Boc)-L-proline served as the optimal chiral derivatising reagent. High-performance liquid chromatography failed to adequately determine diastereomeric excess (de) of resolved diastereomers. Variable temperature, 1 H NMR and 2D EXSY spectroscopic analyses of proline-derivatised diastereomers were successfully employed to characterise equilibrating rotamers of resolved diastereomers and determine their de. Integration of resolved resonances corresponding to H3 and H4 of the β-lactam ring served as a quantitative qNMR tool for the calculation of de following resolution.

Background: In the last years, many efforts have been made to find colchicine derivatives with reduced toxicity. Additionally, the deregulation of amino acid uptake by cancer cells provides an opportunity to improve anticancer drug effectiveness. Objective: To design new colchicine derivatives with reduced cytotoxicity and enhanced selectivity by means of introducing aminoacyl groups. Methods: 34 colchicine analogues bearing L- and D-amino acid pendants were synthetized and characterized by NMR, IR and MS techniques. Cytotoxicity and antimitotic properties were assessed by spectrophotometry and cell cycle assays. Oncogene downregulation was studied by RTqPCR whereas in vivo studies were performed in SCID mice. Results: Compounds exhibit high antiproliferative activities at the nanomolar level while being, in general, less cytotoxic than colchicine. Most compounds inhibit the polymerization of tubulin in a way similar to colchicine itself, with L-amino acid derivatives being the most active in the inhibition of tubulin polymerization. All selected compounds caused cell cycle arrest at the G2/M phase when tested at 1 μM. More specifically, Boc-L-proline derivative 6 arrested half of the population and showed one of the highest Selectivity Indexes. Derivatives 1 (Boc-glycine), 27 (D-leucine) and 31 (Boc-glycine-glycine) proved fairly active in downregulating the expression of the c-Myc, hTERT and VEGF oncogenes, with compound 6 (Boc-L-proline) having the highest activity. This compound was shown to exert a potent anti-tumor effect when administered intraperitoneally (LD50 > 100 mg/kg for 6, compared with 2.5 mg/kg for colchicine). Conclusion: Compound 6 offers an opportunity to be used in cancer therapy with less toxicity problems than colchicine.

An efficient route to enantioenriched propargylamines via a three-component alkynylation reaction using cooperative catalysis with a CuI- iPrpyboxdiPh complex and N-Boc-(l)-proline has been accomplished. A variety of functionalized amines, aldehydes, and 2-ethynyl anilines were reacted smoothly at ambient temperature to furnish a wide range of propargylamines in high yields (up to 94%) and excellent enantioselectivities (up to 98% ee). Synthetic utility of the methodology has been demonstrated by transforming the products into various synthetically useful intermediates. Finally, propargylamines were transformed into biologically important (indol-2-yl)methanamines over two steps in good yields (up to 88%) with an excellent level of enantioselectivities (up to 95%).