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The solid-phase synthesis of 1,2,3,4-tetrahydroisoquinoline-3-carboxamides employing carboxyl-supported, o-alkylated tyrosine esters in a Pictet-Spengler reaction is described. Esterification of [4-(hydroxyphenyl)thiomethyl]polystyrene (Marshall resin) with ethers of N-BOC-L-tyrosine using diisopropylcarbodiimide (DIC) and 4-dimethylaminopyridine (4-DMAP) afforded the solid-supported ester derivatives. Removal of the BOC group with trifluoroacetic acid (TFA) afforded the carboxyl-supported tyrosine ester, which was then treated with paraformaldehyde and TFA to afford the desired solid-supported counterpart. Acylation of the secondary amine with arylsulfonyl chlorides followed by reaction with amines resulted in the formation of the desired 2-arylsulfonyl-7-alkoxy-1,2,3,4-tetrahydroisoquinoline-3-carboxamides. Alternatively, the support-bound tetrahydroisoquinoline-3-carboxylate derivatives could be treated with an aldehyde and a reducing agent to give the corresponding support-bound tertiary amine. Exposure of these resin-bound products to amines afforded the corresponding 2-alkyl-7-alkoxy-1,2,3,4-tetrahydroisoquinoline-3-carboxamides after cleavage from the resin. Alternative routes to the desired chemotypes, as well optimization of the conditions for the Pictet-Spengler reaction and the conditions for the acylation and reductive amination of the support-bound secondary amines, are also described. 相似文献
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Alves GA Amato S Anjos JC Appel JA Astorga J Bracker SB Cremaldi LM Dagenhart WD Darling CL Dixon RL Errede D Fenker HC Gay C Green DR Jedicke R Karchin PE Kennedy C Kwan S Lueking LH de Mello Neto JR Metheny J Milburn RH de Miranda JM da Motta Filho H Napier A Passmore D Rafatian A dos Reis AC Ross WR Santoro AF Sheaff M Souza MH Spalding WJ Stoughton C Streetman ME Summers DJ Takach SF Wallace A Wu Z 《Physical review letters》1996,77(12):2392-2395
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LL Handley R Azcón Ruiz Lozano JM CM Scrimgeour 《Rapid communications in mass spectrometry : RCM》1999,13(13):1320-1324
It has long been evident that plant (15)N chiefly reflects the processes which fractionate (15)N/(14)N rather than the (15)N of plant N source(s). It has emerged recently that one of the most important fractionating processes contributing to the whole plant (15)N is the presence/absence, type or species of mycorrhiza, especially when interacting with nutrient deficiency. Ecto- and ericoid mycorrhizas are frequently associated with (15)N-depleted foliar (15)N, commonly as low as -12 per thousand. As shown by the present study, plants having no mycorrhiza, or those infected with various species of arbuscular mycorrhiza (AM)-forming fungi, interact with varying concentrations of soil nitrogen [N] and moisture to enrich plant (15)N by as much as 3.5 per thousand. Hence the lack of a mycorrhiza, or variation in the species of AM-forming fungal associations, can account for about 25% of the usually reported variations of foliar (15)N found in field situations and do so by (15)N enrichment rather than depletion. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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We describe a simple method to measure the top quark mass in the
channel that may be useful in Run II of D? detector. The method is validated by applying it to the Run Ib eμ data. 相似文献
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JM Chatterjee M Saha Sarkar S Bhattacharya P Banerjee S Sarkar RP Singh S Murulithar RK Bhowmik 《Pramana》2001,57(1):165-169
High-spin states of 95,97Mo (Z=42, N=53,55) nuclei have been investigated through 82Se(18O, xn) reaction at Eb=60 MeV. The level scheme in 95Mo has been observed upto ≏ 10 MeV in the present experiment. The level structure shows mainly single particle character.
In 97Mo, the ground state level sequence has been extended to ≏ 4.5 MeV while the previous information had been up to 2.4 MeV.
A negative parity band built on 1437 keV (11/2−) excited state has been extended to 5.5 MeV. The structure seems to show a coexistence of single particle and collective
modes of excitation. Properties of both the nuclei have been compared with shell model calculations using OXBASH. 相似文献
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