- Solvent-freeN-Boc deprotection byex situgeneration of hydrogen chloride gas
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An efficient, scalable and sustainable method for the quantitative deprotection of thetert-butyl carbamate (N-Boc) protecting group is described, using down to near-stoichiometric amounts of hydrogen chloride gas in solvent-free conditions. We demonstrate theex situgeneration of hydrogen chloride gas from sodium chloride and sulfuric acid in a two-chamber reactor, introducing a straightforward method for controlled and stoichiometric release of HCl gas. The solvent-free conditions allow deprotection of a wide variety ofN-Boc derivatives to obtain the hydrochloride salts in quantitative yields. The procedure obviates the need for any work-up or purification steps providing an uncomplicated green alternative to standard methods. Due to the solvent-free, anhydrous conditions, this method shows high tolerance towards acid sensitive functional groups and furnishes expanded functional group orthogonality.
- De Borggraeve, Wim M.,Gilles, Philippe,Van Mileghem, Seger,Verschueren, Rik H.
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supporting information
p. 5782 - 5787
(2021/07/12)
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- L-Alanine halogenides with L-alanine L-alaninium dimeric cation
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Crystalline salts l-alanine l-alaninium chloride (I) l-alanine l-alaninium bromide (II) and l-alanine l-alaninium iodide (III) were obtained, which have dimeric cations in the structure. The salts crystallize in the monoclinic crystal system with the space group P21 (Z = 4). l-Alanine··· l-alaninium dimers are realized via rather short O–H?O hydrogen bonds between carboxyl and carboxylate groups with the O?O distances equal to 2.421(2), 2.423(2) ? in (I), 2.437(10), 2.413(8) ? in (II) and 2.421(5), 2.442(5) ? in (III) at 200 K. The salts (I) and (II) are isotypic, while the salt (III) has different packing so the structure is distinct. The infrared and Raman spectra and the crystal structures of these compounds are discussed. Besides, we obtained for the first time a new simple salt l-alaninium iodide.
- Ghazaryan,Giester,Fleck,Petrosyan
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p. 428 - 441
(2018/05/03)
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- L-Tryptophan l-tryptophanium chloride
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l-Tryptophan l-tryptophanium chloride is a new salt with (A?A+) type dimeric cation. It crystallizes in the monoclinic system (space group P21, Z = 2). The asymmetric unit contains one zwitterionic l-tryptophan molecule, one l-tryptophanium cation and one chloride anion. The dimeric cation is formed by a OH?O hydrogen bond with the O?O distance equal to 2.5556(18) ?. The infrared and Raman spectra of the crystal are studied and compared with the spectra of l-tryptophanium chloride.
- Ghazaryan,Fleck,Petrosyan
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p. 743 - 750
(2015/02/19)
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- Isolation and structural determination of the antifouling diketopiperazines from marine-derived Streptomyces praecox 291-11
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Marine derived actinomycetes constituting 185 strains were screened for their antifouling activity against the marine seaweed, Ulva pertusa, and fouling diatom, Navicula annexa. Strain 291-11 isolated from the seaweed, Undaria pinnatifida, rhizosphere showed the highest antifouling activity and was identified as Streptomyces praecox based on a 16S rDNA sequence analysis. Strain 291-11 was therefore named S. praecox 291-11. The antifouling compounds from S. praecox 291-11 were isolated, and their structures were analyzed. The chemical constituents representing the antifouling activity were identified as (6S,3S)-6-benzyl-3-methyl-2,5-diketopiperazine (bmDKP) and (6S,3S)-6-isobutyl-3- methyl-2,5-diketopiperazine (imDKP) by interpreting the nuclear magnetic resonance and high-resolution mass spectroscopy data. Approximately 4.8mg of bmDKP and 3.1 mg of imDKP were isolated from 1.2 g of the S. praecox 291-11 crude extract. Eight different compositions of culture media were investigated for culture, the TBFeC medium being best for bmDKP and TCGC being the optimum for imDKP production. Two compounds respectively showed a 17.7 and 21 therapeutic ratio (LC50/EC50) to inhibit zoospores, and two compounds respectively showed a 263 and 120.2 therapeutic ratio to inhibit diatoms.
- Cho, Ji Young,Kang, Ji Young,Hong, Yong Ki,Baek, Hyo Hyun,Shin, Hyoun Woong,Kim, Myoung Sug
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experimental part
p. 1116 - 1121
(2012/10/07)
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- Cyclopeptides and polyketides from coral-associated fungus, Aspergillus versicolor LCJ-5-4
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Three new cyclopentapeptides, versicoloritides A-C (1-3), a new orcinol tetramer, tetraorcinol A (4), and two new lactones, versicolactones A and B (5 and 6) together with three known metabolites, diorcinol, glyantrypine, and cordyol C were isolated from the fermentation broth of the coral-associated fungus Aspergillus versicolor LCJ-5-4. Their structures were elucidated by spectroscopic and chemical methods. The new compounds 1-4 were evaluated for their radical-scavenging activity and antimicrobial activity against Staphylococcus aureus, Escherichia coli, Enterobacter aerogenes, Bacillus subtilis, Pseudomonas aeruginosa, and Candida albicans and cytotoxicity against P388 and Hela cell lines. Compound 4 showed weak radical-scavenging activity against the DPPH radical with an IC50 value of 67 μM.
- Zhuang, Yibin,Teng, Xiancun,Wang, Yi,Liu, Peipei,Wang, Hui,Li, Jing,Li, Guoqiang,Zhu, Weiming
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experimental part
p. 7085 - 7089
(2011/10/09)
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- Hydration of amino acids from ultrasonic measurements
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In this paper the results of compressibility of aqueous solutions of amino acids in water and in aqueous HCl and NaOH solutions at 25 °C are presented. The effect of the charged protonated amino groups and deprotonated carboxylic groups on the hydration number was tested. The idea of additivity of the hydration number with the constituents of the solute molecule was successfully applied and discussed.
- Burakowski, Andrzej,Gliński, Jacek
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experimental part
p. 12157 - 12161
(2011/01/11)
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- Novel cyclopeptide and unique flavone from Desmos rostrata. Total synthesis of desmorostratone
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Two new compounds, a cyclic peptide desmocyclopeptide (1) and a special flavone desmorostratone (2) were isolated from the stem bark of Desmos rostrata, along with two known compounds, desmosdumotins B (3) and C (4). Their structures were established on the basis of the spectral data, including mass spectrometry and 2D NMR. The total synthesis of desmorostratone (2) was performed in order to confirm its structure as well as that of desmosdumotin C (4), which was a tautomeric mixture in the solution. Finally, cytotoxity of these compounds were evaluated. Desmosdumotin C (4) displayed a moderate inhibition activity against KB cell line with an IC50 of 19.2 μM, whereas the other products showed a weak inhibition against the same cell line target.
- Nguyen, Ngoc Tuan,Pham, Van Cuong,Litaudon, Marc,Guéritte, Fran?oise,Bodo, Bernard,Nguyen, Van Tuyen,Nguyen, Van Hung
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experimental part
p. 7171 - 7176
(2009/12/24)
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- (R)- and (S)-3-hydroxy-4,4-dimethyl-1-phenyl-2-pyrrolidinone as chiral auxiliaries in the enantioselective preparation of α-amino acids
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rac-α-Amino acids (rac-1a-d) were formally deracemized by a four-step reaction sequence: (a) protection of the amino function as the phthalimido derivative; (b) acyl chloride formation; (c) diastereoselective reaction with the chiral auxiliaries (R)- or (S)-3-hydroxy-4,4-dimethyl-1-phenyl-2- pyrrolidinone, (R)- or (S)-3; and (d) acid hydrolysis to deprotect both the ester and phthalimido functions. Diastereoselectivities of the intermediate esters 4 were good (82-96% d.e.), except for the case of 4b (41% d.e.), the precursor of valine. The main diastereoisomer of esters 4 was (αR,3S)- or (αS,3R)-, except for 4d: in this case, working at -78°C, the (αR,3R)- diastereoisomer was the main product, which epimerizes easily at the α- position when at room temperature. Acid hydrolysis of esters 4 directly gave the deprotected α-amino acids, with little or no epimerization at the α- position of the α-amino acid and complete recovery of the chiral auxiliary. Only (αR,3R)-4d on acid hydrolysis partially epimerized at the α-position. Moreover, some α-amino acids and their N,N-dibenzyl derivatives were obtained by dynamic kinetic resolution of diastereoisomeric mixtures of α- bromo esters 5 derived from the chiral auxiliaries (R)- or (S)-3 during reaction with dibenzylamine.
- Camps, Pelayo,Perez, Francesc,Soldevilla, Nuria,Borrego, Miguel A.
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p. 493 - 509
(2007/10/03)
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- Empirical rules for the enantiopreference of lipase from Aspergillus niger toward secondary alcohols and carboxylic acids, especially α-amino acids
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Lipase from Aspergillus niger (ANL, Amano lipase AP) catalyzes enantioselective hydrolysis and acylation reactions. To aid in the design of new applications of this lipase, we propose two empirical rules that predict which enantiomer reacts faster. For secondary alcohols, a rule proposed previously for other lipases also works for ANL, but with lower reliability (77%, 37 of 48 examples). For carboxylic acids, we examined both crude and partially-purified ANL because commercial ANL contains contaminating hydrolases. Partial purification removed a contaminating amidase and increased the enantioselectivity of ANL toward many α-amino acids, including cyclic amino acids. Unlike other lipases, ANL readily accepts positively-charged substrates and shows the highest enantioselectivity towards α-amino acids. Although a rule based on the sizes of the substituents could not predict the fast-reacting enantiomer, a rule limited to α-amino acids did predict the fast-reacting enantiomer. We estimate that the charged α-amino group contributes a factor of 40-100 (ΔΔ≠ = 2.2-2.7 kcal/mol) to the enantioselectivity of ANL towards carboxylic acids.
- Janes, Lana E.,Kazlauskas, Romas J.
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p. 3719 - 3733
(2007/10/03)
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- Lipophilic oligopeptides with immunomodulating activity
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New, small and structurally simple immunomodulating oligopeptides are disclosed. The oligopeptides of this invention possess a long, lipophilic alkyl chain. These immunomodulating oligopeptides can be used in conjunction with anti-viral or anti-cancer agents in the treatment of human and animal diseases. Processes for the syntheses of immunomodulating chemicals are also disclosed.
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- Synthesis of L and D α-amino acids from chiral amidals
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A new synthesis of D- and L-alanine is described, by means of the mercury cyclisation of the chiral amidal obtained from the reaction of 1,3,5-tri-(S)-phenylethylhexahydrotriazine and acryloyl chloride.
- Amoroso, Rosa,Cardillo, Giuliana,Tomasini, Claudia
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p. 6412 - 6416
(2007/10/02)
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- Asymmetric Synthesis Catalyzed by Chiral Ferrocenylphosphine-Transition-Metal Complexes. 8. Palladium-Catalyzed Asymmetric Allylic Amination
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Chiral ferrocenylphosphine ligands, represented by (R)-N-methyl-N--1-ethylamine ((R)-(S)-1a), which have a pendant side chain bearing a hydroxy group at the terminal position, were designed and used successfully for palladium-catalyzed asymmetric allylic amination of allylic substrates containing a 1,3-disubstituted propenyl structure (RCH=CHCH(X)R: R = Ph, Me, n-Pr, i-Pr; X = OCOOEt, OCOMe, OP(O)Ph2, etc.).Reaction of the allylic substrates with benzylamine in the presence of a palladium catalyst prepared in situ from Pd2(dba)3 and (R)-(S)-1a gave high yields of amination products (RCH=CHC*H(NHCH2Ph)R: >97percent ee (R) for R = Ph, 73percent ee (S) for R = Me, 82percent ee (S) for R = n-Pr, and 97percent ee (S) for R = i-Pr).The allylamines were converted into optically active amino acids and their derivatives.The high stereoselectivity of the ferrocenylphosphine ligand is expected to be caused by an attractive interaction between the terminal hydroxy group on the ligand and the incoming amine, which directs the nucleophilic attack on one of the ?-allyl carbons.The key role of the hydroxy group was supported by an X-ray structure analysis of a ?-allylpalladium complex and (31)P NMR studies.It was demonstrated that the pendant side chain on the ferrocenylphosphine ligand is directed toward the reaction site on palladium and the terminal hydroxy group is located at the position close to one of the ?-allyl carbon atoms and that ?-allyl group on the palladium coordinated with the ferrocenylphosphine 1a adopts one of the two possible conformational isomers with high selectivity (20/1) in an equilibrium state.
- Hayashi, Tamio,Yamamoto, Akihiro,Ito, Yoshihiko,Nishioka, Eriko,Miura, Hitoshi,Yanagi, Kazunori
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p. 6301 - 6311
(2007/10/02)
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- ENANTIOSELECTIVE SYNTHESES OF α-AMINO ACIDS FROM 10-SULFONAMIDO-ISOBORNYL ESTERS AND DI-t-BUTYL AZODICARBOXYLATE
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Successive treatment of chiral esters 7 with LDA/Me3SiCl and di-t-butyl azodicarboxylate/TiCl4 and Ti(OiPr)4 gave N,N-di-t-butoxycarbonylhydrazinoesters 11 which on deacylation, hydrogenolysis, transesterification and acidic hydrolysis furnished (2S)-α-amino acid hydrochlorides 13 in good overall yields, high enantiomeric purity and with efficient recovery of the alcohol auxiliary 4.Experimental evidence for the configuration and conformation of the intermediate O-silyl ketene acetals 1 is provided.
- Oppolzer, Wolfgang,Moretti, Robert
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p. 5541 - 5552
(2007/10/02)
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- CHLOROTRIMETHYLSILANE-PHENOL AS A MILD DEPROTECTION REAGENT FOR THE TERT-BUTYL BASED PROTECTING GROUPS IN PEPTIDE SYNTHESIS
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Efficient deprotection of the tertbutyl urethane group by 1 M Me3SiCl- 1 M and 3 M-phenol reagents is described.
- Kaiser, Emil,Tam, James P.,Kubiak, Teresa M.,Merrifield, R. B.
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p. 303 - 306
(2007/10/02)
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- A STEREOSELECTIVE SYNTHESIS OF N-BOC-α-AMINO ALCOHOLS AND α-AMINO ACIDS
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A sterteoselective synthesis of N-Boc-α-amino alcohols and α-amino acids via the addition of Grignard reagents to the chiral electrophilic glycine equivalent α-bromo-N-Boc-glycine(-)phenylmenthylester is described.
- Ermert, Philipp,Meyer, Jsabella,Stucki, Christoph,Schneebeli, Joerg,Obrecht, Jean-Pierre
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p. 1265 - 1268
(2007/10/02)
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- The Use of Crown Ethers in Peptide Chemistry. Part 1. Syntheses of Amino Acid Complexes with the Cyclic Polyether 18-Crown-6 and their Oligomerisation in Dicyclohexylcarbodi-imide-containing Solutions
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The synthesis of amino acid complexes with the cyclic polyether 18-crown-6 and their solubility properties in organic solvents are described.Oligo homo-amino acid peptides have been prepared using the crown ether complexes and dicyclohexylcarbodi-imide as coupling agent.The mechanism leading to the formation of the oligopeptides has been discussed and proved to involve the transferring of one N-H proton from the crown ether complex to the carbodi-imide nitrogen.
- Maascagni, Paolo,Hyde, Carolyn B.,Charalambous, Mario A.,Welham, Kevin J.
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p. 323 - 328
(2007/10/02)
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- Enantioselective Synthesis of α-Amino Acids from 10-(Aminosulfonyl)-2-bornyl Esters and Di(tert-butyl) Azodicarboxylate
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Successive treatment of chiral esters 1 with LiN(i-Pr)2/Me3SiCl and di(tert-butyl) azodicarboxylate/TiCl4/Ti(i-PrO)4 gave N,N'-dihydrazino esters 9 which on deacylation, hydrogenolysis, transesterification, and acidic hydrolysis furnished (2S)-α-amino acids 6 in high enantiomeric purity with efficient recovery of the auxiliary alcohol 7.
- Oppolzer, Wolfgang,Moretti, Robert
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p. 1923 - 1926
(2007/10/02)
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