Reaction of Chiral Nucleophiles with Pyridinium Compounds. Total Synthesis of the Indole Alkaloids (−)‐Isovallesiachotamine and (+)‐Vallesiachotamine

Abstract

Abstract The addition of the chiral nucleophiles Na‐ 2 and Li‐ 5 to pyridinium compounds 1 and the subsequent ring closure (Pictet‐Spengler cyclization) to indoloquinolizines 3a and 7b , respectively, proceed stereoselectively (d.e. for 3a : 54%; for 7b : ≥95%). Proof for the absolute configuration of these products is provided by their CD spectral data and the transformation of 7b into the indole alkaloids (+)‐vallesiachotamine [(Z)‐ 6 ] and (‐)‐isovallesiachotamine [( E )‐ 6 ].