methyl (3R)-3-[(2-bromo-1-oxooctyl)oxy]-tetradecanoate → (2R)-5-hexyl-4-hydroxy-2-undecyl-2,3-dihydropyran-6-one

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

In a 500 mL 3-necked round bottom flask fitted with a Claisen head with N2 inlet, a West condenser, a thermocouple-J-KEM controller and an addition funnel was added a solution of tert-butylmagnesium chloride (341 mL of a 1.0 M solution, 341 mmole, 3 equiv.) at about 60° C. Methyl-(R)-3-(2′-bromo-1′-oxooctyloxy)tetradecanoate (52.6.0 g, 113.5 mmole, 1 equiv.) (“bromodiester”) and 25 mL of dry THE were added to an addition funnel. The bromodiester mixture was slowly added to the t-BuMgCl/THF mixture at reflux over about one hour. The reaction mixture was sampled at 1 and 2 hours at about 60° C. (resulting in 90 and 91% area normalized gas chromatography (AN GC) analysis, respectively). After 2 hours the resulting reaction mixture was cooled and concentrated on a roto-evaporator to about ⅓ to about ½ the original volume. The resulting syrupy mixture was taken up in about 250 mL of toluene (or an ether, such as methyl tert-butyl ether and the like; a hydrocarbon, such as hexane, heptane, and the like; or mixtures thereof) and added to a mixture containing 250 mL of toluene, 75 mL of 10% HCl in a 1 L jacketed flask keeping the quenched solution below 30° C. The aqueous layer was removed. The organic layer washed one time with 50 mL of 1.0 N HCl solution. The aqueous layer was removed, the organic layer washed one time with 50 mL of water, dried over magnesium sulfate, filtered and concentrated. This resulted in a gel-like solid residue. The residue was dissolved in 250 mL of ethyl acetate at 40° C. The ethyl acetate was removed on the roto-evaporator. The resulting crude off-white solid (42.4 g) was slurried up in about 100 mL of hexane and cooled to 0° C., filtered and rinsed with 50 mL of cold hexane followed by another 25 mL of cold hexane. The isolated white solids were air dried under vacuum for about 1 to 2 hours resulting in 31.4 g of (6R)-3-hexyl-5,6-dihydro-4-hydroxy-6-undecyl-pyran-2-one (78.4% yield).

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