Reaction of the methyl ester of ustilic acid A (15,16-dihydroxypalmitic acid) with a methyl Grignard, oxidation of the glycol grouping, bromination, and hydrogenolysis produced 15-methylhexadecanoic acid. A series of 15-keto acids resulted from reaction of the amide of ustilic acid A with the appropriate Grignard reagent followed by oxidation of the glycol grouping. Infrared absorption characteristics of these compounds are described.
Methanolysis of ustilagic acid and hydrolysis of the methyl esters formed yielded a crystalline acidic fraction which was essentially a mixture of two substances termed the ustilic acids A and B. The acids were separated as their iso-propylidene derivatives. The ustilic acids cocrystallize to mixtures with melting points intermediate between those of the pure compounds. Conversion of ustilic acid A, m.p. 112–113 °C, [α]D −8° in methanol, which made up about 70% of the mixture, by hydrogenolysis to palmitic acid, by oxidation with chromic oxide to pentadecanedioic acid, and by lead tetraacetate oxidation followed by hydrogenation to 15-hydroxypentadecanoic acid showed the substance to be an optically active form of 15,16-dihydroxyhexadecanoic acid. Conversion of ustilic acid B, m.p. 140–141 °C, [α]D−10° in methanol, by sodium bismuthate oxidation followed by hydrogenation to 1,14-dihydroxytetradecane, by chromic acid oxidation of its methyl ester followed by hydrolysis of the product, and peroxide oxidation of the α-keto acid thus formed to tetradecanedioic acid, and by hydrogenolysis of the C2-carbon atom through a series of reactions to ustilic acid A, showed the substance to be an optically active form of 2,15,16-trihydroxy-hexadecanoic acid. Optically active forms of 2,15-dihydroxypentadecanoic and 2-hydroxypentadecanoic acids were prepared from ustilic acid B. Application of certain empirical rules of rotation to derivatives of these 2-hydroxyacids showed them to possess the D-configuration. Reduction of ustilic acid B with lithium aluminum hydride gave meso-1,2,15,16-tetrahydroxyhexadecane. Thus, ustilic acid B was the 2D,15D,16-trihydroxyhexadecanoic acid and the ustilic acid A was the 15D,16-dihydroxyhexadecanoic acid. Several derivatives of the above described acids were prepared.