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With Novozyme 435 (from Candida antarctica immobilized on acrylic resin); Amberlyst A-21; In toluene; at 20℃; for 15.0h;Enzymatic reaction;Product distribution / selectivity;
Example 28; Preparation of Retinyl Palmitate in the Presence of Amberlyst A-21; Retinyl acetate (1.00 g; 3.04 mmol) was dissolved in 8.5 mL of toluene and palmitic acid (1.56 g; 6.09 mmol; 2.0 equiv) was added followed by 120 mg of Novozyme 435 and 0.5g of dried Amberlyst A-21. The reaction mixture was stirred at RT for 15 h, at which point a sample was removed and analyzed by HPLC, indicating 89.2% conversion to retinyl palmitate with 9.1% retinyl acetate and 1.7% retinol. The reaction mixture was filtered and concentrated, then concentrated twice with heptane (10 mL each). The residue was dissolved in heptane (15 mL) and washed with 2×20 mL with a 1:1 mixture of 10% aqueous potassium carbonate and methanol. The organic layer was washed further with a mixture of saturated sodium bicarbonate (2.5 mL), water (7.5 mL), and methanol (10 mL), dried (sodium sulfate) and concentrated to afford 1.25 g (78%) of a yellow oil. Analysis of this product indicated 91.2% retinyl palmitate (HPLC area percent), 0.4 wt % palmitic acid, and 0.2% retinol. HPLC (4.6×150 mm Zorbax SB-C8 column [Agilent], 3.5mu thickness, methanol eluent, detection at 350 nm): tR 5.52 min (retinyl palmitate); tR 2.32 min (retinyl acetate); tR 2.08 min (retinol).
With novozyme 435; In toluene; at 20℃; for 20.0h;Schlenk technique; Inert atmosphere; Enzymatic reaction;
General procedure: Retinyl esters were synthesized via an enzyme-catalyzed transesterification (19) as follows. Into a dry Schlenk flask, retinyl acetate (33 mg, 0.10 mmol), Novozyme 435 (120 mg), and AberlystA-21 (50 mg) were suspended in dry toluene (5 ml). The reaction mixture was stirred under an atmosphere of N2 , and five equivalents (0.50 mmol) of the appropriate acid (palmitic, stearic, linoleic, or oleic) were added. After 20 h at room temperature, the reaction mixture was filtered and the solvent was removed under reduced pressure to give a mixture (approximately 1:4) of the desired retinyl ester and unreacted acid. The resulting mixtures were used without further purification as LC/MS/MS standards for the corresponding retinyl esters.
With sodium hydroxide; In methanol; at 55℃; under 11.2511 - 16.5017 Torr; for 3.0h;Large scale;
To 3000 kg of the compound of formula (la) which is known as Vitamin A acetate, in its crystalline form, 2750 kg of compound of formula (I la) which is known as methyl palmitate have been added. Afterwards 10 kg of NaOH have been dissolved in about 60 I of methanol, which was then added to the mixture of Vitamin A acetate and methyl palmitate. This reaction mixture was heated up to 55C and the pressure was reduced to about 1500 - 2200 Pa. The reaction time was about 3 hours. During this process the main side product (methyl acetate) was removed continuously by distillation. The reaction was stopped by the addition of water and CO2. Afterwards the compound of formula (Ilia) which is known as Vitamin A palmitate was isolated from the reaction solution by extraction. The yield of compound of formula (Ilia) was 96%.
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