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Synthesis of (−)‐Hobartine and Related Indole Alkaloids
Author(s) -
Darbre Tamis,
Nossbaumer Cornelius,
Borschberg HansJürg
Publication year - 1984
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19840670417
Subject(s) - chemistry , ethylamine , stereoselectivity , imine , indole test , nonane , yield (engineering) , amine gas treating , stereochemistry , organic chemistry , catalysis , materials science , metallurgy
An improved method for obtaining optically pure ( S )‐(l‐ p ‐menthen‐8‐yl)amine ( 12 ) has led to expedient syntheses of two hypothetical biogenetic intermediates on the way to aistoteline ( 7 ), namely ( S )‐( N )‐(l‐ p ‐menthen‐8‐yl)‐2‐(3‐indolyl)ethylamine ( 3 ) and ( S )‐( N )‐(l‐ p ‐menthen‐8‐yl)‐2‐(3‐indolyl)ethylideneamine ( 4 ). The latter has been transformed into (−)‐hobartine ( 6 ) in 64% yield via a stereoselective biomimetic cyclization by treatment with HCOOH. This unambiguous synthesis establishes the hitherto unknown absolute configuration of (−)‐hobartin ( 6 ). Several model cyclization reactions of N ‐substituted α‐(terpen‐8‐yl)imine derivatives yielding unsaturated 3azabicyclo [3.3.1]nonane compounds are described.