[OH:1][C:2]1[CH:7]=[CH:6][C:5]([SH:8])=[CH:4][CH:3]=1.C[O-].[Na+].[CH3:12][C:13]([CH3:22])([CH3:21])[C:14]#[C:15][C:16]([O:18]CC)=[O:17].I[CH:24]([CH2:26][CH3:27])[CH3:25].[OH-].[K+]>CO.O>[CH3:25][CH:24]([O:1][C:2]1[CH:7]=[CH:6][C:5]([S:8][C:14]([C:13]([CH3:12])([CH3:21])[CH3:22])=[CH:15][C:16]([OH:18])=[O:17])=[CH:4][CH:3]=1)[CH2:26][CH3:27]
A solution of p-hydroxythiophenol (64.4 g of 98% pure material, 0.5 mole) in methanol (50 mL) was added dropwise to sodium methoxide (252 mL of a 25% solution in methanol) in a 1 liter, three-neck, round-bottomed flask which had been cooled to 0° C. The resultant reaction mixture was warmed to room temperature, stirred for 1 hour, then again cooled using an ice bath. Ethyl 4,4-dimethylpent-2-ynoate (78 g of 99% pure material, 0.5 mole, prepared in Part A above) was then added dropwise to the reaction mixture over a period of 1.5 hours. The ice bath was then removed, and the reaction mixture was allowed to warm to room temperature and stirred for 2 hours. It was then again cooled, using an ice bath, and 2-iodobutane (110.5 g, 0.6 mole) was added. After the addition had been completed, the resultant mixture was heated to reflux for 3 hours, allowed to stand overnight, and again cooled with an ice bath. Further quantities of sodium methoxide (57 mL of a 25% solution) and 2-iodobutane (46 mL, 0.4 mole) were added, and the reaction mixture was heated at reflux for 3 hours. The process of cooling, addition of sodium methoxide and 2-iodobutane, and heating to reflux was then repeated. The reaction mixture was then cooled to room temperature, potassium hydroxide (100 mL of a 45% aqueous solution) and water (100 mL) were added, and the reaction mixture was heated to 50°-60 ° C. for 2 hours. The volume of the solution was then reduced by about 50%, using a rotary evaporator, after which the concentrated solution was diluted with water (500 mL) and extracted with hexanes. The aqueous layer was cooled and acidified with cold concentrated hydrochloric acid. The material which precipitated (consisting of a mixture of 3-[4-[but-2-oxy]phenylthio]-4,4-dimethylpent-2-enoic acid and dealkylated material, 4,4-dimethyl-3-[4-hydroxyphenylthio]pent-2-enoic acid) was separated and washed with water. The dealkylated material was separated by dissolving the residue in dichloromethane and filtering (the yield of this undesired material was 29.5 g, 23%). The filtrate was concentrated under reduced pressure to give the desired acid (106 g, 68% yield).
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