Investigations into spiroketal synthesis and identification

The spiroketal ring system is found in a wide variety of naturally occurring compounds originating from insects, plants, fungi, bacteria, or marine organisms. These natural products exhibit a wide variety of structural complexities in addition to important pharmacological properties. The purpose of this research was to develop synthetic methods for spiroketal synthesis along with methods for the identification of spiroketal containing compounds.; For the first part of this investigation, we attempted to develop new synthetic methodologies for spiroketal synthesis directed toward the spiroketal subunit of reveromycin A. The first synthetic study investigated both the intermolecular and intramolecular radical substitution of a selenium-substituted spiroketal ring system. The second synthetic study involved epoxidation of a spiroketal ring system followed by the attempted epoxide ring opening with a variety of reagents. The final synthetic study focused on the formation of a spirolactone ring system.; The second part of this research focused on the use of tandem mass spectrometry for structural confirmation of oligomycin A and avermectin Bla as well as detection of avermectin B1a and B1b in environmental matrices. The APCI-MS/MS spectrum of oligomycin A was obtained and shows evidence of two major fragmentation ions. In order to ascertain the further fragmentation of these ions, APCI-MS/MS/MS experiments were conducted on each major product ion. The fragmentation pathways of oligomycin A were determined using APCI-MS/MS/MS techniques. The final investigation explored both the mass spectral fragmentation patterns of avermectin B1a as well as the detection of avermectin B1a and B1b in environmental matrices by tandem mass spectrometry. The mass spectral fragmentation pathways were determined for avermectin B1a using APCI-MS/MS techniques. Automated extraction techniques were developed for the measurement of avermectin residues in soil samples, while the use of SPME technology was successfully employed for the extraction of the avermectins from water samples. A very precise APCI-MS/MS method was developed for the detection of both avermectin B1a and B1b.