After
the structure originally proposed for nitraraine was shown
to be incorrect by total synthesis, the alternative structure <b>5</b> was recently suggested for the alkaloid on biosynthetic
grounds and by comparison with the <sup>1</sup>H NMR data of tangutorine.
The unambiguous synthesis of <b>5</b> is reported from tryptophanol
and ketodiester <b>6</b>, via oxazoloquinolone lactam <b>7</b>. However, the melting point and <sup>1</sup>H NMR data of <b>5</b> did not match those reported for the natural product
