- Organocatalytic Enantioselective Pictet-Spengler Approach to Biologically Relevant 1-Benzyl-1,2,3,4-Tetrahydroisoquinoline Alkaloids
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(Figure Presented) A general procedure for the synthesis of 1-benzyl-1,2,3,4-tetrahydroisoquinolines was developed, based on organocatalytic, regio- and enantioselective Pictet-Spengler reactions (86-92% ee) of N-(o-nitrophenylsulfenyl)-2-arylethylamines with arylacetaldehydes. The presence of the o-nitrophenylsulfenyl group, together with the MOM-protection in the catechol part of the tetrahydroisoquinoline ring system, appeared to be a productive combination. To demonstrate the versatility of this approach, 10 biologically and pharmaceutically relevant alkaloids were prepared using (R)-TRIP as the chiral catalyst: (R)-norcoclaurine, (R)-coclaurine, (R)-norreticuline, (R)-reticuline, (R)-trimemetoquinol, (R)-armepavine, (R)-norprotosinomenine, (R)-protosinomenine, (R)-laudanosine, and (R)-5-methoxylaudanosine.
- Ruiz-Olalla, Andrea,Würdemann, Martien A.,Wanner, Martin J.,Ingemann, Steen,Van Maarseveen, Jan H.,Hiemstra, Henk
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p. 5125 - 5132
(2015/05/27)
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- Synthesis of (+)-O-methylthalibrine by employing a stereocontrolled Bischler-Napieralski reaction and an electrochemically generated diaryl ether
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An efficient electrochemical four-step route was developed for the preparation of diaryl ether derivatives by using halogenation and dehalogenation processes in addition to electrochemical phenolic oxidation and reduction reactions. The synthesis of (+)-O
- Kawabata, Yuki,Naito, Yu,Saitoh, Tsuyoshi,Kawa, Kohei,Fuchigami, Toshio,Nishiyama, Shigeru
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- Enantioselective synthesis of tetrahydroprotoberberines and bisbenzylisoquinoline alkaloids from a deprotonated α-aminonitrile
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Under controlled conditions, 6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline- 1-carbonitrile can be quantitatively deprotonated in the α-position. Its alkylation directly furnishes 3,4-dihydroisoquinolines which can serve as starting materials for the preparation of various alkaloids. Here, the preparation of the benzylisoquinolines (+)-laudanidine, (+)-armepavine, and (+)-laudanosine as well as the tetrahydroprotoberberines ( - )-corytenchine and ( - )-tetrahydropseudoepiberberine using Noyori's asymmetric transfer hydrogenation are described. The dimeric alkaloids (+)-O-methylthalibrine and (+)-tetramethylmagnolamine were obtained from nonracemic precursors in Ullmann diaryl ether syntheses.
- Blank, Nancy,Opatz, Till
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p. 9777 - 9784
(2012/01/30)
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- THE BIOSYNTHESIS OF THE ALKALOIDS OF CISSAMPELOS PAREIRA LINN
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Tracer experimets show that the bisbenzylisoqunoline alkaloid,(S,R)-hayatidin (10) is stereospecifically biosynthesized in young Cissampelos pareira Linn plants by intermolecular oxidativ coupling of (S)-(5)-and (R)-(3)-N-methylcoclaurines whereas (R,R)-isochondrodendrine (14) and (R,R)-bebeerine (12) are formed in the plants by oxidative dimerization of (R)-N-methyl-coclaurine (3).
- Bhakuni,Dewan S.,Jain,Sudha,Chaturvedi,Rekha
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p. 3975 - 3982
(2007/10/02)
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- Kalashine, a novel type aporphine-benzylisoquinoline alkaloid
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Berberis orthobotrys produces the new dimer kalashine (1), together with the previously reported pakistanamine (2) and pakistanine (3). Kalashine is the first aporphine-benzylisoquinoline known to be substituted at C-11. Acid catalyzed rearrangement of pa
- Hussain, S.Fazal,Shamma, Maurice
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p. 3315 - 3318
(2007/10/02)
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