- The enantiospecific, stereospecific total synthesis of the ring-A oxygenated sarpagine indole alkaloids (+)-majvinine, (+)-10-methoxyaffinisine, and (+)-Na-methylsarpagine, as well as the total synthesis of the Alstonia bisindole alkaloid macralstonidine
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The first stereospecific, enantiospecific total synthesis of the ring-A oxygenated sarpagine indole alkaloids (+)-Na-methylsarpagine (8), (+)-majvinine (14), and (+)-10-methoxyaffinisine (49), as well as the first total synthesis of the Alstonia bisindole alkaloid macralstonidine (9), has been accomplished. This approach employed the Schoellkopf chiral auxiliary for the stereospecific construction of the desired D-(+)-tryptophan unit required for the asymmetric Pictet-Spengler reaction. In addition, the strategy was doubly convergent for the enolate-mediated Pd0 coupling process and the asymmetric Pictet-Spengler reaction can be employed to synthesize both macroline (2) and Na-methylsarpagine (8), the coupling of which provides macralstonidine (9). This approach to ring-A substituted alkoxyindole alkaloids should find wide application for the synthesis of other alkaloids for it is stereospecific and either enantiomer can be prepared with ease.
- Zhao, Shuo,Liao, Xuebin,Wang, Tao,Flippen-Anderson, Judith,Cook, James M.
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p. 6279 - 6295
(2007/10/03)
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- Regiospecific Bromination of 3-Methylindoles with NBS and Its Application to the Concise Synthesis of Optically Active Unusual Tryptophans Present in Marine Cyclic Peptides
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A regiospecific bromination of substituted 3-methylindoles at either the C(3) alkyl moiety or the C(2) position was achieved via a free radical bromination or electrophilic process, respectively. The regiospecificity of the bromination could be controlled by variation of both the substituent and the N(1) protecting group on the indole ring. In addition, enantiospecific syntheses of 5-methoxytryptophan (20) and 5-hydroxy-6-chlorotryptophan (21c) as well as concise syntheses of optically active 2-bromotryptophan ethyl esters 26a,b or their substituted derivatives in three steps from bifunctional dibromoindoles were achieved via the above regiospecific process.
- Liu, Ruiyan,Zhang, Puwen,Gan, Tong,Cook, James M.
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p. 7447 - 7456
(2007/10/03)
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- Regiospecific bromination of 3-methylindoles with N-bromosuccinimide
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The regiospecific bromination of various substituted 3-methylindoles at either C(2) or the C(3) alkyl moiety was accomplished via an electrophilic of free radical bromination process to provide intermediates for indole alkaloid total synthesis. The regiospecificity of the bromination could be controlled by variation of both the substituent and the N(1) protecting group on the indole ring.
- Zhang, Puwen,Liu, Ruiyan,Cook, James M.
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p. 3103 - 3106
(2007/10/02)
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- Enantiospecific synthesis of 5-methoxy-D(+)- or L(-) tryptophan
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A method for the enantiospecific synthesis of 5-methoxy-D(+)-tryptophan 8 or the L(-)-optical antipode is described. This procedure can be scaled up and performed without the need for extensive chromatographic separations. It provides for the first time t
- Zhang,Cook
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p. 3883 - 3900
(2007/10/03)
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