Biochemistry of the Ustilaginales: Viii. The Structures and Configurations of the Ustilic Acids

Abstract

Methanolysis of ustilagic acid a r~d hydrolysis of the methyl esters for~lled 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 isopropylidene derivatives. The ustilic acids cocrystallize to mixtures with melting points intermediate between those of the pure compounds. Conversion of ustilic acid A, 1n.p. 112-113" C., [O]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 a n optically active form of 15,16-dihyd<oxyhexadecanoic acid. Conversion of ustilic acid B, m.p. 140-141" C., [aID -10" in methanol, by sodium bisnluthate oxidation followed by hydrogenation to 1,14-dihydroxytetradecane, by chromic acid oxidation of its methyl ester followed by hydrolysisof the product, and peroxideoxidation of the a-keto acid thus formed to tetradecanedioic acid, and by hydrogenolysis of the C2-carbon atom through a series cf reactions to ustilic acid A, showed the substance to be an optically active form of 2,15,16-trihydrosyhexadecarloic 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 -~~n f i g l l r a t i~n .Reduction of ustilic acid B with lithium aluminum hydride gave ineso-1,2,15,16-tetrahydroxyhesadecane. Thus, ustilic acid B was the 2~,15~,16-trihydrosyhesadecanoic acid and the ustilic acid A was the 15~,lG-dihydroxyhexadecanoic acid. Several derivatives of the above described acids were prepared.

Ustilago maydis secondary metabolism—From genomics to biochemistry

“…The substance was termed ustilagic acid and turned out to be a mixture of glycolipids derived from cellobiose lipid (Lemieux, 1951). The cellobiose disaccharide is glycosidically linked to the terminal hydroxyl group of either 2,15,16-trihydroxypalmitic acid (ustilagic acid B) or 15,16-dihydroxy-palmitic acid (ustilagic acid A) (Lemieux, 1953). The sugar moiety is further acetylated and esterified with either b-hydroxy-hexanoic or b-hydroxy-octanoic acid (Fig.…”

In vitro interactions between Fusarium verticillioides and Ustilago maydis through real-time PCR and metabolic profiling

“…Evidence that those compounds directly affect the plant-pathogen interaction and disease development is ambiguous, leading to the speculation that they play ecological roles in competition against other microorganisms (Bacon et al, 2004;Duffy et al, 2004;Keyser et al, 1999;Toyoda et al, 1988). The basidiomycete U. maydis and closely related smut fungi produce a variety of secondary compounds such as ustilagic acid and mannosylerythrol glycolipids but their role as virulence factors or during ecological interactions with other microbes is unclear (Hewald et al, 2005;Lemieux, 1953;Teichmann et al, 2007).…”

Identification of a Gene Cluster for Biosynthesis of Mannosylerythritol Lipids in the Basidiomycetous Fungus Ustilago maydis

“…U. maydis is unique among fungal producers of biosurfactants because it produces two structurally different classes of glycolipids. Ustilagic acid is a cellobiose lipid in which the disaccharide is O-glycosidically linked to the -hydroxyl group of 2,15,16-trihydroxy-or 15,16-dihydroxyhexadecanoic acid (22). In addition to ustilagic acid, which displays antibiotic activity (9), U. maydis secretes an extracellular oil which is heavier than water and consists of mannosylerythritol lipids (MELs) (1,6,21).…”