Chemical Transformation of Hydrolyzed Fumonisin B₁ to Hydrolyzed Fumonisin B₂

The fumonisins, a series of sphingosine-analog mycotoxins produced by the ubiquitous corn contaminant Fusarium moniliforme, are an important food safety concern because they are tumor promoters with sufficient chemical stability to persist through normal food processing. Removing propane-1,2,3-tricarboxylic acid side chains produces hydrolyzed fumonisins (HF), including HFB₁ and HFB₂, which retain biological activity. Detection of hydrolyzed fumonisins in food products has created a need for efficient methods to prepare them for use as analytical standards. In the present study conversion of the more abundant HFB₁ to HFB₂ was accomplished by selectively protecting the hydroxyl groups to be retained as the bis(acetonide), deoxygenating the remaining free hydroxyl, and removing the blocking groups. Deoxygenation was accomplished by two methods: (i) free radical-initiated homolytic cleavage of the O-phenoxythiocarbonyl ester in the presence of tributyltin hydride and (ii) LiA1H₄ reduction of the tosylate ester.