Enantioselective Syntheses of Syributin 1 and Novel C-Glycosidic Elicitors Syringolides 1 and 2

Concise enantioselective syntheses of syributin 1 ( 3 ) and the novel nonproteinaceous C-glycosidic elicitors syringolides 1 and 2 ( 1 and 2, respectively), isolated from Pseudomonas syringae pv. tomato, are described. Syributin 1 was synthesized in one step by the Sharpless catalytic asymmetric dihydroxylation (AD reaction) of (1‘ E )-3-(3‘-(octanoyloxy)-1‘-propenyl)but-2-en-4-olide ( 13 ) in 72% yield with >98% ee. Furthermore, alkylation of (1‘ R,2‘ R )-3-[1‘-( tert -butyldimethylsiloxy)-2‘,3‘-(isopropylidenedioxy)propyl]but-2-en-4-olide ( 20 ), prepared from (1‘ E )-3-[3‘-( tert -butyldimethylsiloxy)-1‘-propenyl]but-2-en-4-olide ( 11 ) by the AD reaction, with hexanal or octanal by Jefford's procedure at the α position to the lactone carbonyl group gave adduct 21 or 22 in good yield. Oxidation of 21 or 22, followed by removal of the protecting groups, provided syringolide 1 or 2, respectively.