Syringolides 1 and 2 were isolated from P. syringar pv. tomato in 1993 by Sims et al. as the first nonproteinaceous specific elicitors of a plant hypersensitive response (HR). They also proposed the biosynthetic pathway of syringolides from the corresponding <i>b</i>-ketoacids and D-xylulose. There have been several reports for the total synthesis of syringolides, and most of the syntheses have been achieved through the butenolide intermediate with various alcohol protecting groups.<br/>To synthesize syringolides with the right stereogenic centers, some group used the biomimetic pathway, which started from D-xylulose. Although D-xylulose is commercially available, it is costly, and it is a drawback of this biomimetic synthesis pathway. Therefore, to avoid the use of D-xylulose, many groups have been employed chiral starting materials as the source of asymmetry including various carbohydrates. The availability of D-xylulose limits the biomimetic synthetic pathway. To prepare D-xylulose, isomerization from D-xylose to D-xylulose has been developed first by enzymes last two decades. In the past several years, isomerization with inorganic catalysts has been reported using Lewis acid catalysts. In contrast to the isomerization, chemical synthesis seems challenging like the other carbohydrates since it has multiple hydroxyl groups and stereocenters. Enzymes were found as efficient C–C bond construction, but the methods are still limited , and it is beneficial to develop a new synthetic methodology to prepare D-xylulose. We will report the synthesis of D-xylulose via Wittig reaction and asymmetric diolization from readily available chemicals, hydroxyl acetone, and ethylene glycol. The strategy is straightforward, and the key of this synthesis is the choices of protecting groups. We then achieved the formal synthesis of syringolide 1 from the obtained protected D-xylulose.

Formal synthesis of syringolide 1

256th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.