Phytophthora mating hormone α1
Phytophthora are plant pathogens responsible for a number of important plant diseases. There are two mating types, A1 and A2. A hormone α1 secreted by A1 type induces oospores in A2 type while hormone α2 secreted by A2 type induces oospores in A1 type.
Figure 1. Leaf and stem blight caused by Phytophthora nicotianae on lily
Figure 2. Picture of a Phytophthora oospore
The Phytophthora mating hormone α1 was isolated and structurally characterized by Ojika and coworkers in 2005, however the relative and absolute configuration was not assigned.1 The lack of stereochemical knowledge has prompted us to pursue its total synthesis. We have previously synthesized four stereoisomers of hormone α1 as a mixture of two compounds each.2 Our current focus is to synthesize a complete stereoisomer library of hormone α1 through FMS. We plan to use the double tagging technique, where in two of the stereocenters will be tagged by fluorous TIPS groups while OEG group will be used to tag the third stereocenter. The key reactions are the two modified Julia olifination reactions to couple the fragment 3 to fragments 1 and 2.
4 and 5 are separately carried on to Hydrogenation, OEG demixing, OEG deprotection, oxidation, Fluorous demixing, and deprotection to provide 8 stereoisomers.