Enzymatic synthesis of tryptamine and its halogen derivatives selectively labeled with hydrogen isotopes

Nine isotopomers of tryptamine and its halogen derivatives, labeled with deuterium, tritium in side chain, i.e., [(1R)-²H]-, [(1R)-³H]-, 5-F-[(1R)-²H]-, 5-F-[(1R)-³H]-, 5-Br-[(1R)-²H]-, double labeled [(1R)-²H/³H]-, 5-F-[(1R)-²H/³H]-, and ring labeled [4-²H]-, and [5-²H]-tryptamine, were obtained by enzymatic decarboxylation of l-Trp and its appropriate derivatives in deuteriated or tritiated media, respectively. Intermediates: [5′-²H]-l-Trp used for further decarboxylation was synthesized by enzymatic coupling of [5-²H]-indole with S-methyl-l-cysteine, and [4′-²H]-l-Trp was obtained by isotope exchange ¹H/²H of the authentic l-Trp dissolved in heavy water induced by UV-irradiation. Doubly labeled [(1R)-²H/³H]- and 5-F-[(1R)-²H/³H]-tryptamine were obtain by decarboxylation of l-Trp or [5′-F]-l-Trp carried out in ²H³HO incubation medium.     

Synthesis of L-tryptophan labeled with hydrogen isotopes in the indole ring

The isotopomers of L-tryptophan (L-Trp) labeled with hydrogen isotopes in the indole ring were obtained by isotope exchange method. Heavy and tritiated water were used as the sources of stable and radioactive label. Three isotopomers, i.e., [4′-²H]-L-Trp, [4′-³H]-L-Trp, and doubly labeled [4′-²H/³H]-L-Trp were synthesized by isotope exchange enhanced by irradiation with a mercury discharge lamp. The indole whole ring labeled isotopomers, i.e., [2′,4′,5′,6′,7′-²H₅]-L-, [2′,4′,5′,6′,7′-³H₅]-L-, and doubly labeled [2′,4′,5′,6′,7′-²H/³H]-L-Trp were synthesized by isotope exchange between L-Trp and D₂O or DTO in the presence of deuteriated trifluoroacetic acid.     

Synthesis of isotopomers of <Emphasis Type="SmallCaps">l</Emphasis>-DOPA and dopamine labeled with hydrogen isotopes in the side chain

The enzymatic synthesis of three isotopomers of l-DOPA labeled with deuterium and tritium at α carbon atom was elaborated. These compounds were converted into [(1S)-²H]–, [(1S)- ³H]–, and doubly labeled [(1S)-²H/³H]-dopamines using enzyme tyrosine decarboxylase. Doubly labeled (1R) isotopologue, i.e., [(1R)-²H/³H]-dopamine, was afforded by enzymatic decarboxylation of authentic l-DOPA carried out in deuteriated and tritiated incubation medium.     

Safety-catch linker strategies for the production of radiopharmaceuticals labeled with positron-emitting isotopes

A novel synthetic stratetegy for compounds labeled with the positron-emitting isotope carbon-11 is described. The use of precursors attached to a solid support via safety-catch linkers allows selective release of radiolabeled material, leaving unreacted precursor attached to the support. Two different linkers demonstrate the application to the preparation of radiolabeled N-alkyl tertiary amines and N-alkylsulfonamides. This technique is expected to lead to more widespread use of positron emission tomography for the in vivo analysis of compound behavior.     

Enzymatic syntheses of carbon-14 labeled isotopomers of L-phenylalanine

Convenient and efficient processes are described for the synthesis of L-enatiomers of phenylalanine specifically labeled with carbon-14 in 1-, 2-, and 3-positions of side chain. The method consists of the preparation of the proper isotopomers of cinnamic acid labeled with ¹⁴C and their conversion into L-phenylalanine using enzyme activity. The combined chemical and enzymatic approach allows to produce three different isotopomers of phenylalanine in pure L-optical form labeled with ¹⁴C.     

The synthesis of labeled sterols

This review presents a discussion of methods for the chemical synthesis of sterols labeled with hydrogen and carbon isotopes.Institute of Bioorganic Chemistry, Belarus National Academy of Sciences, 220141 Belarus', Minsk, Ul. Akad. Kuprevicha, 5/2. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 413–441, July–August, 1999.     

Enzymatic synthesis of monolaurin

The aim of this study was to produce monolaurin utilizing a commercial immobilized lipase (Lipozyme IM-20; Novo Nordisk, Bagsvaerd, Denmark) through the direct esterification of lauric acid and glycerol in a solvent-free system. The influence of fatty acid/glycerol molar ratio, temperature, and Lipozyme (IM-20) concentration on the molar fraction of monolaurin were determined using an experimental design. The best conditions employed were 55°C, lauric acid/glycerol molar ratio of 1.0, and 3.0% (w/w) enzyme concentration. The final product, obtained after 6 h of reaction, was 45.5% monolaurin, 26.8% dilaurin, 3.1% trilaurin, and 24.6% lauric acid. The reusability of the enzyme was also studied.     

Regioselective aromatic ring functionalization of dopamine analogues

The selective aromatic ring functonalization of tetramethyl dopamine 2 at C₂ and C₅ was achieved via alkyllithium-induced carbanion formation at r.t. and −78° , respectively. The C-6 substitution was affected via palladium acetate mediated cyclometallation.     

Enzymatic synthesis of prebiotic oligosaccharides

Prebiotic oligosaccharides are nondigestible carbohydrates that can be obtained by enzymatic synthesis. Glucosyltransferases can be used to produce these carbohydrates through an acceptor reaction synthesis. When maltose is the acceptor a trisaccharide composed of one maltose unit and one glucose unit linked by an alpha-1,6-glycosidic bond (panose) is obtained as the primer product of the dextransucrase acceptor reaction. In this work, panose enzymatic synthesis was evaluated by a central composite experimental design in which maltose and sucrose concentration were varied in a wide range of maltose/sucrose ratios in a batch reactor system. A partially purified enzyme was used in order to reduce the process costs, because enzyme purification is one of the most expensive steps in enzymatic synthesis. Even using high maltose/sucrose ratios, dextran and higher-oligosaccharide formation were not avoided. The results showed that intermediate concentrations of sucrose and high maltose concentration resulted in high panose productivity with low dextran and higher-oligosaccharide productivity.     

生物催化在非天然寡糖合成中的应用

酶已经成为现代有机合成中一种不可或缺的工具。近年来人们在克隆技术，微生物学以及蛋白纯化方面的研究成果为我们提供了越来越多的生物催化剂，酶最初用于天然产物的合成，而今其在非天然化合物中的应用更引起了生物化学家的广泛关注。酶催化反应可以使不加保护的高官能团化底物进行条件温和，环境友好地转化，得到具有高度化学、区域和立体选择性的产物。本文对近年来糖基转移酶在糖生物学中的应用，特别是其在利用Leloir方法合成非天然寡糖中的应用作一简要回顾。     

Enzymatic synthesis of cyclic triterpenes

This review covers recent advances in the chemistry and enzymology of squalene cyclase and oxidosqualene cyclase. The enzymatic cyclizations of squalene and oxidosqualene are the most remarkable steps in the biosynthesis of sterols and triterpenes. The polyenes are converted to various polycyclic triterpenes by different enzyme systems employing only small modification of the active-site. Recent crystallographic and structure-based mutagenesis studies as well as utilization of chemically synthesized active-site probes have begun to reveal intimate structural details of the enzyme-templated cyclization reactions. 126 References are cited.     

爱滋病病毒中肽段的酶促合成

为了进一步研究酶促合成在多肽合成中的实际应用,选择合成了爱滋病病毒(人类免疫缺损病毒,HIV-I)的gp41中氨基酸序列598-609的三个肽段,该部分是HIV-I中的2个抗原决定簇部分,H-Leu-Glg-Leu-Trp-Glg-cgs-Ser-Glg-Lgs-Leu-Ile-Cgs-OH可以作为抗原来检测HIV抗体.