@unpublished{pittir9966,
           month = {January},
           title = {Fluorous Mixture Synthesis and Structure Assignment of Petrocortyne A and Its Stereoisomers},
          author = {Bin Sui},
            year = {2010},
        keywords = {fluorous mixture synthesis; Mosher ester; NMA ester; petrocortyne; structure assignment; TOCSY},
             url = {http://d-scholarship-dev.library.pitt.edu/9966/},
        abstract = {Petrocortyne A was isolated from the marine sponge Petrosia sp. by Shin and Jung in 1998 and 1999, respectively. Both groups assigned the absolute configuration of the natural product, but the assignments do not consistent with the reported optical rotations. Using the fluorous mixture synthesis (FMS), we have synthesized four stereoisomers of petrocortyne A to determine the absolute configuration. In the FMS, the stereoisomeric starting materials were tagged with different fluorous TIPS groups and mixed together. The resulting mixture was taken through a series of steps to make the fluorous-tagged products, which were separated by fluorous HPLC followed by desilylation to provide four pure products. Second-generation fluorous TIPS tags were synthesized and used in the FMS. Both Mosher and NMA ester methods were studied during the synthesis. The study showed that NMA ester method is superior to Mosher method for the assignment of absolute configuration of stereocenter C14.Comparison of optical rotations of the four synthetic and two natural samples showed that both natural samples had the C3-S configuration. Comparison of spectra of Mosher derivatives of the synthetic and natural samples showed that both natural samples had the 3S,14S configuration. At the same time, the use of the Mosher rule has been validated for assigning the challenging C14 stereocenter of petrocortyne A. A "shortcut" variant in which only one Mosher ester is made was developed and can also be used for assignment of this stereocenter.}
}