Synthesis of the microbial elicitor syringolide 2 multiply labelled with deuterium

Multiply-deuterated syringolide 2 3 was prepared from D-xylulose and 8-bromooctanoic acid by a convergent route based on our previously reported biomimetic synthesis of this microbial elicitor. Key steps were the thermal acylation of the anisylidene-protected sugar 6 with the C-octenoyl Meldrum's acid derivative 7b, the one-pot triple-cyclisation of the xylulose beta-ketoester 9b to 9,10-dehydrosyringolide 2 (10), and the introduction of multiple deuterium labels in the side chain by catalytic exchange and reduction. The route is applicable to the synthesis of tritium labelled syringolide 2 4.