1
|
Shou K, Zhang Y, Ji Y, Liu B, Zhou Q, Tan Q, Li F, Wang X, Lu G, Xiao G. Highly stereoselective α-glycosylation with GalN 3 donors enabled collective synthesis of mucin-related tumor associated carbohydrate antigens. Chem Sci 2024; 15:6552-6561. [PMID: 38699257 PMCID: PMC11062124 DOI: 10.1039/d4sc01348d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Accepted: 04/01/2024] [Indexed: 05/05/2024] Open
Abstract
Mucin-related tumor-associated carbohydrate antigens (TACAs) are important and interesting targets for cancer vaccine therapy. However, efficient access to a library of mucin-related TACAs remains a challenging task. One of the key issues is the challenging construction of α-GalNAc linkages. Here, we report highly stereoselective α-glycosylation with GalN3N-phenyl trifluoroacetimidate donors, which features excellent yields, outstanding stereoselectivities, broad substrate scope and mild reaction conditions. This method is successfully applied to highly stereoselective synthesis of GalN3-α-O-Ser, which served as the common intermediate for collective synthesis of a wide range of TACAs including TN antigen, STN antigen, 2,6 STF antigen, 2,3 STF antigen, glycophorin and cores 1-8 mucin-type O-glycans. In particular, the rationale for this highly stereoselective α-glycosylation is provided for the first time using DFT calculations and mechanistic studies, highlighting the crucial roles of reagent combinations (TMSI and Ph3PO) and the H-bonding directing effect of the N3 group.
Collapse
Affiliation(s)
- Kunxiu Shou
- State Key Laboratory of Phytochemistry and Natural Medicines, Kunming Institute of Botany, University of Chinese Academy of Sciences, Chinese Academy of Sciences 132 Lanhei Road Kunming 650201 China
| | - Yunqin Zhang
- State Key Laboratory of Phytochemistry and Natural Medicines, Kunming Institute of Botany, University of Chinese Academy of Sciences, Chinese Academy of Sciences 132 Lanhei Road Kunming 650201 China
| | - Yujie Ji
- School of Chemistry and Chemical Engineering, Shandong University Jinan Shandong 250100 China
| | - Bin Liu
- State Key Laboratory of Phytochemistry and Natural Medicines, Kunming Institute of Botany, University of Chinese Academy of Sciences, Chinese Academy of Sciences 132 Lanhei Road Kunming 650201 China
| | - Qingli Zhou
- State Key Laboratory of Phytochemistry and Natural Medicines, Kunming Institute of Botany, University of Chinese Academy of Sciences, Chinese Academy of Sciences 132 Lanhei Road Kunming 650201 China
| | - Qiang Tan
- State Key Laboratory of Phytochemistry and Natural Medicines, Kunming Institute of Botany, University of Chinese Academy of Sciences, Chinese Academy of Sciences 132 Lanhei Road Kunming 650201 China
| | - Fuying Li
- Department of Chemistry, Kunming University 2 Puxing Road Kunming 650214 China
| | - Xiufang Wang
- Department of Chemistry, Kunming University 2 Puxing Road Kunming 650214 China
| | - Gang Lu
- School of Chemistry and Chemical Engineering, Shandong University Jinan Shandong 250100 China
| | - Guozhi Xiao
- State Key Laboratory of Phytochemistry and Natural Medicines, Kunming Institute of Botany, University of Chinese Academy of Sciences, Chinese Academy of Sciences 132 Lanhei Road Kunming 650201 China
| |
Collapse
|
2
|
Yang J, Xie D, Ma X. Recent Advances in Chemical Synthesis of Amino Sugars. Molecules 2023; 28:4724. [PMID: 37375279 DOI: 10.3390/molecules28124724] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 06/06/2023] [Accepted: 06/07/2023] [Indexed: 06/29/2023] Open
Abstract
Amino sugars are a kind of carbohydrates with one or more hydroxyl groups replaced by an amino group. They play crucial roles in a broad range of biological activities. Over the past few decades, there have been continuing efforts on the stereoselective glycosylation of amino sugars. However, the introduction of glycoside bearing basic nitrogen is challenging using conventional Lewis acid-promoted pathways owing to competitive coordination of the amine to the Lewis acid promoter. Additionally, diastereomeric mixtures of O-glycoside are often produced if aminoglycoside lack a C2 substituent. This review focuses on the updated overview of the way to stereoselective synthesis of 1,2-cis-aminoglycoside. The scope, mechanism, and the applications in the synthesis of complex glycoconjugates for the representative methodologies were also included.
Collapse
Affiliation(s)
- Jian Yang
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Demeng Xie
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China
| | - Xiaofeng Ma
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| |
Collapse
|
3
|
Zhu S, Li J, Loka RS, Song Z, Vlodavsky I, Zhang K, Nguyen HM. Modulating Heparanase Activity: Tuning Sulfation Pattern and Glycosidic Linkage of Oligosaccharides. J Med Chem 2020; 63:4227-4255. [PMID: 32216347 DOI: 10.1021/acs.jmedchem.0c00156] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Heparanase cleaves polymeric heparan sulfate (HS) molecules into smaller oligosaccharides, allowing for release of angiogenic growth factors promoting tumor development and autoreactive immune cells to reach the insulin-producing β cells. Interaction of heparanase with HS chains is regulated by specific substrate sulfation sequences. We have synthesized 11 trisaccharides that are highly tunable in structure and sulfation pattern, allowing us to determine how heparanase recognizes HS substrate and selects a favorable cleavage site. Our study shows that (1) N-SO3- at +1 subsite and 6-O-SO3- at -2 subsite of trisaccharides are critical for heparanase recognition, (2) addition of 2-O-SO3- at the -1 subsite and of 3-O-SO3- to GlcN unit is not advantageous, and (3) the anomeric configuration (α or β) at the reducing end is crucial in controlling heparanase activity. Our study also illustrates that the α-trisaccharide having N- and 6-O-SO3- at -2 and +1 subsites inhibited heparanase and was resistant toward hydrolysis.
Collapse
Affiliation(s)
- Sanyong Zhu
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Jiayi Li
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Ravi S Loka
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Zhenfeng Song
- Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, Michigan 48201, United States
| | - Israel Vlodavsky
- Cancer and Vascular Biology Research Center, Rappaport Faculty of Medicine, Technion, Haifa 31096, Israel
| | - Kezhong Zhang
- Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, Michigan 48201, United States
| | - Hien M Nguyen
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| |
Collapse
|
4
|
Zhu S, Samala G, Sletten ET, Stockdill JL, Nguyen HM. Facile triflic acid-catalyzed α-1,2- cis-thio glycosylations: scope and application to the synthesis of S-linked oligosaccharides, glycolipids, sublancin glycopeptides, and T N/T F antigens. Chem Sci 2019; 10:10475-10480. [PMID: 32110337 PMCID: PMC7020787 DOI: 10.1039/c9sc04079j] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 09/30/2019] [Indexed: 01/22/2023] Open
Abstract
Studies of S-linked glycoconjugates have attracted growing interest because of their enhanced chemical stability and enzymatic resistance over O-glycoside counterparts.
Studies of S-linked glycoconjugates have attracted growing interest because of their enhanced chemical stability and enzymatic resistance over O-glycoside counterparts. We here report a facile approach to access α-1,2-cis-S-linked glycosides using triflic acid as a catalyst to promote the glycosylation of a series of thiols with d-glucosamine, galactosamine, glucose, and galactose electrophiles. This method is broadly applicable for the stereoselective synthesis of S-linked glycopeptides, oligosaccharides and glycolipids in high yield and excellent α-selectivity. Many of the synthetic limitations associated with the preparation of these S-linked products are overcome by this catalytic method.
Collapse
Affiliation(s)
- Sanyong Zhu
- Department of Chemistry , Wayne State University , Detroit , Michigan 48202 , USA . ;
| | - Ganesh Samala
- Department of Chemistry , Wayne State University , Detroit , Michigan 48202 , USA . ;
| | - Eric T Sletten
- Department of Chemistry , University of Iowa , Iowa City , Iowa 52242 , USA
| | - Jennifer L Stockdill
- Department of Chemistry , Wayne State University , Detroit , Michigan 48202 , USA . ;
| | - Hien M Nguyen
- Department of Chemistry , Wayne State University , Detroit , Michigan 48202 , USA . ;
| |
Collapse
|
5
|
Sletten ET, Tu YJ, Schlegel HB, Nguyen HM. Are Brønsted Acids the True Promoter of Metal-Triflate-Catalyzed Glycosylations? A Mechanistic Probe into 1,2- cis-Aminoglycoside Formation by Nickel Triflate. ACS Catal 2019; 9:2110-2123. [PMID: 31819822 PMCID: PMC6900934 DOI: 10.1021/acscatal.8b04444] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Metal triflates have been utilized to catalytically facilitate numerous glycosylation reactions under mild conditions. In some methods, the metal triflate system provides stereocontrol during the glycosylation, rather than the nature of protecting groups on the substrate. Despite these advances, the true activating nature of metal triflates remains unclear. Our findings indicated that the in situ generation of trace amounts of triflic acid from metal triflates can be the active catalyst species in the glycosylation. This fact has been mentioned previously in metal triflate-catalyzed glycosylation reactions; however, a thorough study on the subject and its implications on stereoselectivity has yet to be performed. Experimental evidence from control reactions and 19F NMR spectroscopy have been obtained to confirm and quantify the triflic acid released from nickel triflate, for which it is of paramount importance in achieving a stereoselective 1,2-cis-2-amino glycosidic bond formation via a transient anomeric triflate. A putative intermediate resembling that of a glycosyl triflate has been detected using variable temperature NMR (1H and 13C) experiments. These observations, together with density functional theory calculations and a kinetic study, corroborate a mechanism involving triflic acid-catalyzed stereoselective glycosylation with N-substituted trifluoromethylbenzylideneamino protected electrophiles. Specifically, triflic acid facilitates formation of a glycosyl triflate intermediate which then undergoes isomerization from the stable α-anomer to the more reactive β-anomer. Subsequent SN2-like displacement of the reactive anomer by a nucleophile is highly favorable for the production of 1,2-cis-2-aminoglycosides. Although there is a previously reported work regarding glycosyl triflates, none of these reports have been confirmed to come from the counter ion of the metal center. Our work provides supporting evidence for the induction of a glycosyl triflate through the role of triflic acid in metal triflate-catalyzed glycosylation reactions.
Collapse
Affiliation(s)
- Eric T Sletten
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, United Sates
| | - Yi-Jung Tu
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - H Bernhard Schlegel
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - Hien M Nguyen
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| |
Collapse
|
6
|
Li M, Yu F, Yao C, Wang PG, Liu Y, Zhao W. Synthetic and immunological studies on trimeric MUC1 immunodominant motif antigen-based anti-cancer vaccine candidates. Org Biomol Chem 2019; 16:993-999. [PMID: 29345713 DOI: 10.1039/c7ob02976d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Therapeutic vaccines have been regarded as a very promising treatment modality against cancer. Tumor-associated MUC1 is a promising antigen for the design of antitumor vaccines. However, body's immune tolerance and low immunogenicity of MUC1 glycopeptides limited their use as effective antigen epitopes of therapeutic vaccines. To solve this problem, we chose the immune dominant region of MUC1 VNTRs. We designed and synthesized its linear trivalent glycopeptide fragments and coupled the fragments with BSA. Immunological evaluation indicated that the antibodies induced by glycosylated MUC1 based vaccine 11 had a stronger binding than non-glycosylated 10. The novel constructed antigen epitopes have the potential to overcome the weak immunogenicity of natural MUC1 glycopeptides and deserve further research.
Collapse
Affiliation(s)
- Mingjing Li
- State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research, Nankai University, Haihe Education Park, 38 Tongyan Road, Tianjin 300353, P.R. China
| | | | | | | | | | | |
Collapse
|
7
|
Shelke YG, Yashmeen A, Gholap AVA, Gharpure SJ, Kapdi AR. Homogeneous Catalysis: A Powerful Technology for the Modification of Important Biomolecules. Chem Asian J 2018; 13:2991-3013. [PMID: 30063286 DOI: 10.1002/asia.201801020] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2018] [Revised: 07/29/2018] [Indexed: 12/17/2022]
Abstract
Homogeneous catalysis plays an important and ubiquitous role in the synthesis of simple and complex molecules, including drug compounds, natural products, and agrochemicals. In recent years, the wide-reaching importance of homogeneous catalysis has made it an indispensable tool for the modification of biomolecules, such as carbohydrates (sugars), amino acids, peptides, nucleosides, nucleotides, and steroids. Such a synthetic strategy offers several advantages, which have led to the development of new molecules of biological relevance at a rapid rate relative to the number of available synthetic methods. Given the powerful nature of homogeneous catalysis in effecting these synthetic transformations, this Focus Review has been compiled to highlight these important developments.
Collapse
Affiliation(s)
- Yogesh G Shelke
- Department of Chemistry, Indian Institute of Technology, Bombay, Main Gate Road, Powai, Mumbai, 400076, India
| | - Afsana Yashmeen
- Department of Chemistry, Institute of Chemical Technology, Nathalal Parekh Road, Matunga, Mumbai, 400019, India
| | - Aniket V A Gholap
- Department of Chemistry, Institute of Chemical Technology, Nathalal Parekh Road, Matunga, Mumbai, 400019, India
| | - Santosh J Gharpure
- Department of Chemistry, Indian Institute of Technology, Bombay, Main Gate Road, Powai, Mumbai, 400076, India
| | - Anant R Kapdi
- Department of Chemistry, Institute of Chemical Technology, Nathalal Parekh Road, Matunga, Mumbai, 400019, India
| |
Collapse
|
8
|
Affiliation(s)
- Michael Martin Nielsen
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | | |
Collapse
|
9
|
Jiang ZQ, Zhao SQ, Su YX, Liu N, Wu ZQ. Combination of RAFT and Pd(II)-Initiated Isocyanide Polymerizations: A Versatile Method for Facile Synthesis of Helical Poly(phenyl isocyanide) Block and Star Copolymers. Macromolecules 2018. [DOI: 10.1021/acs.macromol.7b02663] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Zhi-Qiang Jiang
- Department of Polymer Science and Engineering,
School of Chemistry and Chemical Engineering, and Anhui Key Laboratory
of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei 230009 Anhui Province, China
| | - Song-Qing Zhao
- Department of Polymer Science and Engineering,
School of Chemistry and Chemical Engineering, and Anhui Key Laboratory
of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei 230009 Anhui Province, China
| | - Yi-Xu Su
- Department of Polymer Science and Engineering,
School of Chemistry and Chemical Engineering, and Anhui Key Laboratory
of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei 230009 Anhui Province, China
| | - Na Liu
- Department of Polymer Science and Engineering,
School of Chemistry and Chemical Engineering, and Anhui Key Laboratory
of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei 230009 Anhui Province, China
| | - Zong-Quan Wu
- Department of Polymer Science and Engineering,
School of Chemistry and Chemical Engineering, and Anhui Key Laboratory
of Advanced Catalytic Materials and Reaction Engineering, Hefei University of Technology, 193 Tunxi Road, Hefei 230009 Anhui Province, China
| |
Collapse
|
10
|
Liu N, Sun RW, Lu HJ, Li XL, Liu CH, Wu ZQ. Synthesis and chiroptical properties of helical polystyrenes stabilized by intramolecular hydrogen bonding. Polym Chem 2017. [DOI: 10.1039/c7py01633f] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Helical polymers with a controlled helicity and a core cross-linked star polymer carrying the helical arms were facilely prepared.
Collapse
Affiliation(s)
- Na Liu
- Department of Polymer Science and Engineering
- School of Chemistry and Chemical Engineering
- and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering
- Hefei University of Technology
- Hefei 23000
| | - Rui-Wen Sun
- Department of Polymer Science and Engineering
- School of Chemistry and Chemical Engineering
- and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering
- Hefei University of Technology
- Hefei 23000
| | - Hao-Jun Lu
- Department of Polymer Science and Engineering
- School of Chemistry and Chemical Engineering
- and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering
- Hefei University of Technology
- Hefei 23000
| | - Xue-Liang Li
- Department of Polymer Science and Engineering
- School of Chemistry and Chemical Engineering
- and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering
- Hefei University of Technology
- Hefei 23000
| | - Chun-Hua Liu
- Department of Polymer Science and Engineering
- School of Chemistry and Chemical Engineering
- and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering
- Hefei University of Technology
- Hefei 23000
| | - Zong-Quan Wu
- Department of Polymer Science and Engineering
- School of Chemistry and Chemical Engineering
- and Anhui Key Laboratory of Advanced Catalytic Materials and Reaction Engineering
- Hefei University of Technology
- Hefei 23000
| |
Collapse
|
11
|
Sletten ET, Ramadugu SK, Nguyen HM. Utilization of bench-stable and readily available nickel(II) triflate for access to 1,2-cis-2-aminoglycosides. Carbohydr Res 2016; 435:195-207. [PMID: 27816838 DOI: 10.1016/j.carres.2016.10.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Revised: 10/10/2016] [Accepted: 10/20/2016] [Indexed: 10/20/2022]
Abstract
The utilization of substoichiometric amounts of commercially available nickel(II) triflate as an activator in the reagent-controlled glycosylation reaction for the stereoselective construction of biologically relevant targets containing 1,2-cis-2-amino glycosidic linkages is reported. This straightforward and accessible methodology is mild, operationally simple and safe through catalytic activation by readily available Ni(OTf)2 in comparison to systems employing our previously in-house prepared Ni(4-F-PhCN)4(OTf)2. We anticipate that the bench-stable and inexpensive Ni(OTf)2, coupled with little to no extra laboratory training to set up the glycosylation reaction and no requirement of specialized equipment, should make this methodology be readily adopted by non-carbohydrate specialists. This report further highlights the efficacy of Ni(OTf)2 to prepare several bioactive motifs, such as blood type A-type V and VI antigens, heparin sulfate disaccharide repeating unit, aminooxy glycosides, and α-GalNAc-Serine conjugate, which cannot be achieved in high yield and α-selectivity utilizing in-house prepared Ni(4-F-PhCN)4(OTf)2 catalyst. The newly-developed protocol eliminates the need for the synthesis of Ni(4-F-PhCN)4(OTf)2 and is scalable and reproducible. Furthermore, computational simulations in combination with 1H NMR studies analyzed the effects of various solvents on the intramolecular hydrogen bonding network of tumor-associated mucin Fmoc-protected GalNAc-threonine amino acid antigen derivative, verifying discrepancies found that were previously unreported.
Collapse
Affiliation(s)
- Eric T Sletten
- Department of Chemistry, University of Iowa, Iowa City, 52242, USA
| | | | - Hien M Nguyen
- Department of Chemistry, University of Iowa, Iowa City, 52242, USA.
| |
Collapse
|
12
|
Li X, Zhu J. Glycosylation via Transition-Metal Catalysis: Challenges and Opportunities. European J Org Chem 2016. [DOI: 10.1002/ejoc.201600484] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Xiaohua Li
- Department of Natural Sciences; University of Michigan-Dearborn; 4901 Evergreen Road 48128 Dearborn Michigan USA
| | - Jianglong Zhu
- Department of Chemistry and Biochemistry and School of Green Chemistry and Engineering; The University of Toledo; 2801 West Bancroft Street 43606 Toledo Ohio USA
| |
Collapse
|
13
|
Peng P, Schmidt RR. An Alternative Reaction Course in O-Glycosidation with O-Glycosyl Trichloroacetimidates as Glycosyl Donors and Lewis Acidic Metal Salts as Catalyst: Acid–Base Catalysis with Gold Chloride-Glycosyl Acceptor Adducts. J Am Chem Soc 2015; 137:12653-9. [DOI: 10.1021/jacs.5b07895] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Peng Peng
- Department of Chemistry, University of Konstanz, D-78457 Konstanz, Germany
| | - Richard R. Schmidt
- Department of Chemistry, University of Konstanz, D-78457 Konstanz, Germany
| |
Collapse
|