The polyketide secondary metabolites spongosoritin A and gracilioethers A-C contain a unique methyl [2(5H)-furanylidene]ethanoate core. A synthetic model of a suspected biosynthetic intermediate to these natural products was constructed in seven steps and 48% overall yield. This model undergoes a facile cyclisation/double dehydration cascade to give the desired furanylidene motif, with the required (2Z) isomer obtained in >90 dr when an ethyl substituent is located at C3′ of the furanylidene.
- Cyclisation/dehydration cascade
- Methyl [2(5H)-furanylidene]ethanoate
- Sodio-lithio dianion enolate