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. Author manuscript; available in PMC: 2017 Aug 21.
Published in final edited form as: J Med Chem. 2015 Apr 17;58(9):3794–3805. doi: 10.1021/jm501984f

Scheme 2.

Scheme 2

Synthesis of tricyclic indole carboxylic acid derivatives

(a) EtOH, H2SO4; (b) TMSCHN2 (2M in hexane), MeOH, benzene; (c) BH3-THF, THF; 20% (d) Dt-BuAD, PPh3, THF; (e) KOH (aq.), THF, 12–45% (six steps); (f) m-CPBA, CH2Cl2, 56–88%.