84094-75-7Relevant academic research and scientific papers
Enantiospecific Total Synthesis of the Sarpagine Related Indole Alkaloids Talpinine and Talcarpine as Well as the Improved Total Synthesis of Alstonerine and Anhydromacrosalhine-methine via the Asymmetric Pictet-Spengler Reaction
Yu, Peng,Wang, Tao,Li, Jin,Cook, James M.
, p. 3173 - 3191 (2007/10/03)
The enantiospecific total synthesis of talpinine 1 and talcarpine 2 has been accomplished from D-(+)-tryptophan in 13 steps (11 reaction vessels) in 10% and 9.5% overall yields, respectively. Moreover, this synthetic approach has been employed for the improved synthesis of alstonerine 3 and anhydromacrosalhine-methine 4 in 12% and 14% overall yield, respectively. A convenient synthetic route for the enantiospecific, stereospecific preparation of the key intermediate (-)-Na-H, Nb-benzyl tetracyclic ketone 15a via the asymmetric Pictet-Spengler reaction on a multihundredgram scale has been developed. A diastereocontrolled (>30:1) anionic oxy-Cope rearrangement and the intramolecular rearrangement to form ring-E and an Nb-benzyl/Nb-methyl transfer reaction also served as key steps. This general approach can now be utilized for the synthesis of macroline/ sarpagine related indole alkaloids and their antipodes for biological screening.
Enantiospecific Formation of Trans 1,3-Disubstituted Tetrahydro-β-carbolines by the Pictet-Spengler Reaction and Conversion of Cis Diastereomers into Their Trans Counterparts by Scission of the C-1/N-2 Bond
Cox, Eric D.,Hamaker, Linda K.,Li, Jin,Yu, Peng,Czerwinski, Kevin M.,Deng, Li,Bennett, Dennis W.,Cook, James M.,Watson, William H.,Krawiec, Mariusz
, p. 44 - 61 (2007/10/03)
The factors which effect the stereoselective formation of trans-1-alkyl-2-benzyl-3-(alkoxycarbonyl)-1,2,3,4-tetrahydro-β-carbolines and trans-3-(alkoxycarbonyl)-1-alkyl-2-(diphenylmethyl)-1,2,3,4-tetrahydro-β- carbolines by the Pictet-Spengler cyclization were examined by heating tryptophan derivatives with aldehydes of varied steric bulk under aprotic and acidic conditions, followed by determination of the ratio of cis to trans diastereomers so formed. The presence of a benzyl group at the Nb-nitrogen atom alters the diastereochemical outcome of this condensation to provide 100% trans stereoselectivity when the cyclization is carried out with cyclohexanecarboxaldehyde. Furthermore, when Nb-(diphenylmethyl)tryptophan isopropyl ester was condensed with aldehydes of any size, trans diastereomers are formed with 100% stereoselectively. The trans Nb-substituted diastereomers are thermodynamically more stable than their cis congeners as shown by equilibration experiments in TFA. Conversion of the cis diastereomers into the more stable trans diastereomers is believed to occur under acidic conditions by cleavage of the carbon (C-1)-nitrogen (N-2) bond with complete retention of configuration at the C-3 stereocenter. Evidence from deuterium exchange experiments as well as optical rotations support this model for epimerization. In addition, when cis diastereomer 66a was allowed to stir in CF3COOD, the trans isomer 66b was isolated in 90% yield, while treatment of cis 66a with CF3COOH/NaBH4 provided a mixture of the ring cleaved [scission across C(1)-N(2) bond] product 67 and the trans isomer 66b. Treatment of 66b (control experiment) with NaBH4/CF3COOH under the same conditions returned only starting trans 66b in excellent yield. The Pictet-Spengler reaction of substrates with sufficiently large substituants, followed by treatment with acid, permits the 100% enantiospecific formation of trans-1,3-disubstituted-1,2,3,4-tetrahydro-β-carbolines for alkaloid total synthesis.
ASYMMETRIC SYNTHESIS OF (1S)-(-)-TRYPARGINE
Shimizu, Masato,Ishikawa, Masayuki,Komoda, Yasuo,Nakajima, Terumi,Yamaguchi, Keiichi,Sakai, Shin-ichiro
, p. 3453 - 3456 (2007/10/02)
(1S)-(-)-Trypargine 8(1a) was synthesized from (1S,3R)-(-)-2-benzyl-3-(methoxycarbonyl)-1,2,3,4-tetrahydro-9H-pyridoindole-1-propionic acid (3a), prepared by the asymmetric Pictet-Spengler reaction of Nb-benzyl-(D)-tryptophan methyl este
