Proof of the Revised Structure

Although we had achieved the synthesis of our target, 1, we were distraught when we realized we had made an unnatural product, not a natural one. Moreover, a very small possibility remained that we had misinterpreted the structural evidence provided by our synthesis, and that Maciel s interpretation of the NMR data was correct. As a result, we decided that we needed to synthesize compound 2 so that we could compare its NMR spectra to those of sacacarin. 

1 was protected as its ketal and reduced with LiAlH4 to diol 37. Reoxidation with NMO and catalytic TPAP provided a mixture of lactones, and deprotection and separation gave 49% 1 and 19% 2. The spectral features of the synthetic 2 were identical to those of sacacarin.1 

Our synthesis of 1 accomplished many of the objectives we had defined at the onset. 

Our synthesis of 1 also achieved some unexpected results. We were able to show that sacacarin had the structure 2, we discerned the origin of the structural misassignment, and we prepared 2 from 1 and confirmed the new structural assignment. 

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