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A New Efficient Route for Multigram Asymmetric Synthesis of Alkannin and Shikonin
Author(s) -
Couladouros Elias A.,
Strongilos Alexandros T.,
Papageorgiou Vassilios P.,
Plyta Zoi F.
Publication year - 2002
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20020415)8:8<1795::aid-chem1795>3.0.co;2-v
Subject(s) - chemistry , yield (engineering) , annulation , enantiomer , combinatorial chemistry , organic chemistry , stereochemistry , catalysis , materials science , metallurgy
A short and convergent approach for the synthesis of alkannin, shikonin and shikalkin is presented. A Hauser‐type annulation of cyanophthalide 26 with enone 7 affords the complete aromatic system in just one step with concomitant attachment of the entire side chain. Subsequent Corey's oxazaborolidine mediated asymmetric reduction of the above advanced intermediate, leads to the required isomer in high enantiomeric excess. Finally, a selective and high yielding deprotection protocol furnishes the title compounds as pure crystalline precipitates. Thus, a multigram synthesis of shikonin, alkannin and shikalkin is achieved in high yield and enantioselectivity.