Enantioselective total synthesis of (+)-lysergic acid, (+)-lysergol, and (+)-isolysergol by palladium-catalyzed domino cyclization of allenes bearing amino and bromoindolyl groups
Enantioselective total synthesis of the biologically important indole alkaloids (+)-lysergol, (+)-isolysergol, and (+)-lysergic acid is described. Key features of these total synthesis include (1) a facile synthesis of a chiral 1,3-amino alcohol via the Pd(0)- and In(I)-mediated reductive coupling reaction between l-serine-derived 2-ethynylaziridine and formaldehyde; (2) the Cr(II)/Ni(0)-mediated Nozaki-Hiyama-Kishi (NHK) reaction of an indole-3-acetaldehyde with iodoalkyne; and (3) Pd(0)-catalyzed domino cyclization of an allene bearing amino and bromoindolyl groups. This domino cyclization enabled direct construction of the C/D ring system of the ergot alkaloids skeleton, as well as the creation of the C5 stereogenic center with transfer of the allenic axial chirality to the central chirality.
Total synthesis of (±)-lysergic acid, lysergol, and isolysergol by palladium-catalyzed domino cyclization of amino allenes bearing a bromoindolyl group
(Chemical Equation Presented) Ergot alkaloids and their synthetic analogs have been reported to exhibit broad biological activity. We investigated direct construction of the C/D ring system of ergot alkaloids based on palladium-catalyzed domino cyclization of amino allenes. With this biscyclization as the key step, total synthesis of (±)-lysergic acid, (±)-lysergol, and (±)-isolysergol was achieved.
Dehydrogenation with Benzeneseleninic Anhydride in the Total Synthesis of Ergot Alkaloids
Investigation of the dehydrogenative conversion of indolines into indoles with benzeneseleninic anhydride (1) resulted in the development of an efficient standardised procedure, which was successfully applied to the final steps in first total synthesis of (+/-)-lysergol (18), (+/-)-isolysergol (27), and (+/-)-elymoclavine (29).
Ninomiya, Ichiya,Hashimoto, Chiyomi,Kiguchi, Toshiko,Naito, Takeaki,Barton, Derek, H. R.,et al.
p. 707 - 713
(2007/10/02)
Dehydrogenation with phenylseleninic anhydride in the total synthesis of ergot alkaloids
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Ninomiya,Hashimoto,Kiguchi,et al.
p. 4187 - 4190
(2007/10/02)
A TOTAL SYNTHESIS OF (+/-)-LYSERGOL, A 9-ERGOLENE TYPE OF ERGOT ALKALOID
According to the synthetic route established on the despyrrole analog of the alkaloid, the first total synthesis of (+/-)-lysergol was completed.
TOTAL SYNTHESIS OF ERGOT ALKALOIDS, (+/-)-ELYMOCLAVINE AND (+/-)-ISOLYSERGOL
Two of the hitherto untouched ergot alkaloids, (+/-)-elymoclavine and (+/-)-isolysergol, were synthesized according to the synthetic route involving enamide photocyclization.