Preparation method of ubenimex side chain_Kain Industrial Additive

Background and overview^[1]

Ubenimex (Bestatin) is a dipeptide compound isolated from the culture medium of Streptomyces olivoreticuli. It was launched in Japan in 1987 as an immune enhancer for the treatment of leukemia. ; Ubenimesi was launched in China in 1998 under the trade name Baishixin. Bestatin has obvious immunomodulatory function and significant anti-tumor activity. Bestatin's impact on the immune system is mainly reflected in its ability to effectively enhance the functions of T and B lymphocytes, while improving the killing activity of natural killer cells (NK). In addition, it can also stimulate the regeneration and differentiation of bone marrow cells by promoting the synthesis of colony-stimulating factors, thereby regulating, enhancing, exciting and restoring the body's immune function. Bestatin can inhibit the invasion of mouse melanoma highly metastatic strain B16BL6; it can also inhibit the formation of luminal structures in HUVECs. In experiments on mouse transplanted tumors, Bestatin was found to inhibit tumor cell metastasis and tumor-induced angiogenesis. Ubenimex, as a small molecule immune enhancer, has been clinically proven to be safe and effective in adjunctive treatment with traditional chemotherapy drugs in the treatment of various cancers such as leukemia, multiple myeloma, myelodysplastic syndromes and other solid tumors. However, single drug use has little effect. The side chain of ubenimex is an intermediate in the synthesis of ubenimex.

Preparation^[2]

The side chain of ubenimex is prepared as follows:

1) The threo racemate of compound (7) (10.0g, 42.1mmol) was dissolved in isopropyl alcohol (50mL), and L-arginine (7.33g, 42.1mmole) was added and dissolved in water ( 25mL), heat to 60~65℃, stir for 30 minutes, then cool to 5~10℃, continue stirring the reaction mixture for 3 hours, pour out the upper layer solution, and disperse the precipitated semi-solid with acetone (50mL), at room temperature After stirring for 48 hours, the crystals were collected by filtration and recrystallized twice with isopropyl alcohol. After vacuum drying at 35~40°C, 6.1g of compound (14) was obtained, with a yield of 35.2%. Dissolve compound (14) (6.1g, 14.8mmole) in water (60mL) at around -10°C, add 1N hydrochloric acid dropwise to pH=2~3, and adjust to pH=5~6 with sodium hydroxide solution. Filter, collect the solid, and obtain 3.3g of compound (9) after vacuum drying at 35~40°C, with a yield of 94.3%.

2) Dissolve compound (9) (3.5g, 14.8mmol) in water (40mL), add hydrochloric acid (3mL), slowly heat to 40~45°C, and then keep the temperature for 2 hours, then add hydrogen to the solution The sodium oxide solution was adjusted to pH=5~6, and then extracted 4 times with dichloromethane. The combined extracts were washed once with saturated brine and dried over anhydrous sodium sulfate. Filter and concentrate the filtrate to obtain 2.7 g of compound (10) with a yield of 93.4%. After testing, compound (10) has: m.p.: 222.5~223.5°C, [α]=+31.9° (C=1, 1NHCl). The prepared compound (10) enters the next step of reaction.

3) Preparation of (2S, 3R)-3-benzyloxycarboxamido-2-hydroxy-4-phenylbutyric acid (11, ubenimex side chain)

Compound (10) (10.0g, 51.2mmol), S-4,6-dimethylpyrimidinyl-2-thiocarboxylic acid benzyl ester (15.4g, 56.1mmol), triethylamine (7.8g, 77.1mmol) was dissolved in dioxane (50mL) and water (50mL), stirred at room temperature for 3 hours, added 140mL water, washed twice with 170mL ethyl acetate, the water layer was adjusted to pH=1~2 with hydrochloric acid, and then Extract twice with 300 mL of ethyl acetate, wash once with water, dry over anhydrous sodium sulfate for 2 hours, and then filter. The filtrate is concentrated to dryness under reduced pressure, then added with petroleum ether and soaked for 2 hours, filtered, and dried to obtain 14.4 g of compound (11). After testing, the obtained compound (11) has: m.p.: 154~155°C, [α]=+82.1° (C=1, AcOH). The prepared compound (11) enters the next step of reaction.