Almazole C, a New Indole Alkaloid Bearing an Unusually 2,5‐Disubstituted Oxazole Moiety, and its putative biogenetic peptidic precursors, from a senegalese delesseriacean seaweed

Abstract

<jats:title>Abstract</jats:title><jats:p>From product isolation and biomimetic synthesis – which also establishes absolute configurations – the known oxazole alkaloids almazoles A ((+)‐<jats:bold>1</jats:bold>) and B ((+)‐<jats:bold>2</jats:bold>) seem to arise in a Senegalese delesseriacean seaweed from, in seuence, the new modified peptide prealmazole C ((+)‐<jats:bold>4</jats:bold>) and the oxazole alkaloid almazole C ((+)‐<jats:bold>3a</jats:bold>). <jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>‐Dimethyl‐<jats:sc>L</jats:sc>‐phenylalaninamide ((+)‐<jats:bold>7</jats:bold>) and the new peptides (+)‐<jats:bold>5</jats:bold> and (+)‐<jats:bold>6</jats:bold>, as well as a series of known small units, are also involved. In all cases, the oxazole ring is peculiarly 2,5‐inserted.