Total synthesis of (±) aspidofractinine

Leuconoxine, Kopsinitarine, Kopsijasmine, and Kopsinone Derivatives from Kopsia

“…The absence of W-coupling to H-21 indicated that oxygenation was likely at C-17. This was further confirmed by comparison of the 13 C NMR data with synthetic racemic 17-oxoaspidofractinine (after correcting for the assignments of the carbon shifts) 34 and 19-oxoaspidofractinine, 35,36 which revealed a close correspondence with the former. Kopsonoline (4) is therefore 17-oxoaspidofractinine, and while the racemic form constitutes one of the intermediate compounds in the synthesis of various aspidofractinine alkaloids, [34][35][36] it is here encountered as an optically active natural product for the first time.…”

Total syntheses of pyrroloazocine indole alkaloids: challenges and reaction discovery

“…The Diels-Alder reaction between an indoline-containing diene and a dienophile has also been widely used in the synthesis of indole alkaloids 23 (Scheme 5). An alternative approach to spiro[indoline-cyclohexanes] is based on C6 ring-closing transformations (Scheme 3d), such as aldol-type reactions, 24,25 olefin metathesis, 26 and Dieckmann condensation. 27,28 The last two approaches were developed by the group of Nishida in the course of the total synthesis of lundurines.…”

Collective Total Synthesis of Aspidofractinine Alkaloids through the Development of a Bischler–Napieralski/Semipinacol Rearrangement Reaction

“…From advanced intermediate 23, a collective synthesis of all four aspidofractinine alkaloids could be achieved. Direct amide reduction of 23 with in situ prepared AlH 3 would produce N-methyl-aspidofractinine (2) Scheme 3. Synthesis the core structure 8.…”