A ring fragmentation and intramolecular azomethine ylide 1,3-dipolar cycloaddition sequence of reactions was successfully used in the preparation of a known (+/-)-cycloclavine precursor in good overall yield. Results of efforts to incorporate the tetrasubstituted cyclopropane ring present in cycloclavine are also discussed. (C) 2013 Elsevier Ltd. All rights reserved.
作者:Nitinkumar D. Jabre、Teruki Watanabe、Matthias Brewer
DOI:10.1016/j.tetlet.2013.10.152
日期:2014.1
A ring fragmentation and intramolecular azomethine ylide 1,3-dipolar cycloaddition sequence of reactions was successfully used in the preparation of a known (+/-)-cycloclavine precursor in good overall yield. Results of efforts to incorporate the tetrasubstituted cyclopropane ring present in cycloclavine are also discussed. (C) 2013 Elsevier Ltd. All rights reserved.
New routes to clavine-type ergot alkaloids. Part 2: Synthesis of the last, so far not yet synthesized member of the clavine alkaloid family, (±)-cycloclavine
Starting from 4-bromo-Uhle's ketone (2), an alkylation step using ethyl 3-methylamino-propionate followed by intramolecular aldol condensation in two steps, transformation of the ester group into a methyl group, and finally cyclopropanation of the 8,9 double bond, resulted in a six-step total synthesis of (±)-cycloclavine (1).