3472-22-8Relevant articles and documents
The ethoxycarbonyl group as both activating and protective group in N-acyl-Pictet-Spengler reactions using methoxystyrenes. A short approach to racemic 1-benzyltetrahydroisoquinoline alkaloids
Bartel, Karin,Bracher, Franz,Geisslinger, Franz,Keller, Marco,Sauvageot-Witzku, Karl,Schaefer, Michael,Urban, Nicole
, p. 2716 - 2725 (2022/01/12)
We present a systematic investigation on an improved variant of the N-acyl-Pictet-Spengler condensation for the synthesis of 1-benzyltetrahydroisoquinolines, based on our recently published synthesis of N-methylcoclaurine, exemplified by the total syntheses of 10 alkaloids in racemic form. Major advantages are a) using ω-methoxystyrenes as convenient alternatives to arylacetaldehydes, and b) using the ethoxycarbonyl residue for both activating the arylethylamine precursors for the cyclization reaction, and, as a significant extension, also as protective group for phenolic residues. After ring closure, the ethoxycarbonyl-protected phenols are deprotected simultaneously with the further processing of the carbamate group, either following route A (lithium alanate reduction) to give N-methylated phenolic products, or following route B (treatment with excess methyllithium) to give the corresponding alkaloids with free N-H function. This dual use of the ethoxycarbonyl group shortens the synthetic routes to hydroxylated 1-benzyltetrahydroisoquinolines significantly. Not surprisingly, these ten alkaloids did not show noteworthy effects on TPC2 cation channels and the tumor cell line VCR-R CEM, and did not exhibit P-glycoprotein blocking activity. But due to their free phenolic groups they can serve as valuable intermediates for novel derivatives addressing all of these targets, based on previous evidence for structure-activity relationships in this chemotype.
Effect of 1-Substitution on Tetrahydroisoquinolines as Selective Antagonists for the Orexin-1 Receptor
Perrey, David A.,German, Nadezhda A.,Decker, Ann M.,Thorn, David,Li, Jun-Xu,Gilmour, Brian P.,Thomas, Brian F.,Harris, Danni L.,Runyon, Scott P.,Zhang, Yanan
, p. 599 - 614 (2015/04/27)
Selective blockade of the orexin-1 receptor (OX1) has been suggested as a potential approach to drug addiction therapy because of its role in modulating the brain's reward system. We have recently reported a series of tetrahydroisoquinoline-based OX1 selective antagonists. Aimed at elucidating structure-activity relationship requirements in other regions of the molecule and further enhancing OX1 potency and selectivity, we have designed and synthesized a series of analogues bearing a variety of substituents at the 1-position of the tetrahydroisoquinoline. The results show that an optimally substituted benzyl group is required for activity at the OX1 receptor. Several compounds with improved potency and/or selectivity have been identified. When combined with structural modifications that were previously found to improve selectivity, we have identified compound 73 (RTIOX-251) with an apparent dissociation constant (Ke) of 16.1 nM at the OX1 receptor and >620-fold selectivity over the OX2 receptor. In vivo, compound 73 was shown to block the development of locomotor sensitization to cocaine in rats. (Chemical Equation Presented).
1,3-benzyl migration in iminium ions: Evidence for a fast free-radical chain reaction
Blank, Nancy,Straub, Bernd F.,Opatz, Till
experimental part, p. 7355 - 7365 (2012/01/06)
The "exocyclic" 1,3-benzyl shift observed in iminium salts derived from 1-benzyl-1,2,3,4-tetrahydroisoquinolines is related to the "endocyclic" Knabe rearrangement. A crossover experiment, isotopic labelling, the study of initiators and inhibitors as well as DFT calculations of gas-phase model structures provide evidence for a free-radical pathway under kinetic entropy control that is not affected by "slow" radical traps. An unexpected rearrangement of methyleneiminium ions derived from 1-benzyl-1,2,3,4-tetrahydroisoquinolines has been investigated by isotopic labelling, trapping experiments and DFT calculations. Theobserved benzyl migration proceeds by an exceptionally fast radical chain reaction closely related to the Knabe reaction.Remarkably, the process is inhibited byneither methyl acrylate nor dioxygen. Copyright
