Fmoc-2-Mercaptobenzothiazole (MBT), for the Introduction of the Fmoc Moiety Free of Side-Reactions

A double side-reaction, consisting in the formation of Fmoc--Ala-OH and Fmoc--Ala-AA-OH, during the preparation of Fmoc protected amino acids (Fmoc-AA-OH) with Fmoc-OSu is discussed. Furthermore, the new Fmoc-2-MBT reagent is proposed for avoiding these side-reactions as well as the formation of the Fmoc-dipeptides (Fmoc-AA-AA-OH) and even tripeptides, which is another important side-reaction when chloroformates such as Fmoc-Cl is used for the protection of the -amino function of the amino acids.

Screening of highly modular sugar-based ligand libraries in the enantioselective C-C coupling reactions

Projecte de recerca elaborat a partir d’una estada a la University of Nottingham, Gran Bretanya, entre març i abril del 2007. Aquest treball s’ha centrat en l’aplicació de compostos derivats de la D-(+)-glucosa, de la D-(+)-fructosa i la D-galactosa com a lligands de catalitzadors homogenis quirals en dos reaccions asimètriques: addició 1,2 a aldehids catalitzada per níquel i addició 1,4 conjugada catalitzada per coure.(veure figura adjunta al final del document). En primer lloc, s’ha estudiat l’aplicació dels compostos L1-L6 a les reaccions d’addició 1,2 a aldehids catalitzades per níquel. S’ha observat que la selectivitat del procés depèn principalment del grup funcional unit a l’esquelet del lligand, de les propietats estèriques del substituent en la funció oxazolina i de l’estructura del substrat. S’ha obtingut fins a un 59% d’excés enantiomèric utilitzant el precursor de catalitzador que conté el lligand L3a. En segon lloc, aquest treball descriu l’aplicació de les tres famílies de compostos (L1-L11) com a lligands en la reacció d’addició 1,4 catalitzada per coure de compostos organometàl•lics a diferents enones amb diferents propietats estèriques. L’ús de les llibreries de compostos fosfit-oxazolina (L1-L5) i fosfit-fosforamidit (L6) han proporcionat bones enantioselectivitats (fins a 80%) en l’addició de reactius de trialquilalumini a diferents enones. En canvi, la llibreria de compostos monofosfit (L7-L11) ha mostrat bones activitats però enantioselectivitats fins a 57%.

Divergent Reactions to Globalization: Labor Unions and the Nafta and the EU Enlargement Process

The 1990s witnessed the launching of two ambitious trade regionalization plans, the Nafta and EU enlargement to Central and Eastern Europe. In contrast to previous projects for the creation or expansion of regional trade blocs, these two projects concerned states at dramatically different levels of economic development: The Nafta involved the very wealthy economies of Canada and the USA and the significantly poorer economy of Mexico, whereas EU enlargement involved the very wealthy economy of the 15 member-state European Union and the significantly poorer economies of former Communist states in Central and Eastern Europe. Ultimately, the Nafta and EU enlargement are responses to the challenges of globalization. Paradoxically, however, they have been met with radically different societal reactions in the wealthy partners that participated in the launching of these processes. This paper focuses on the reaction by labor unions on both sides of the Atlantic. I conclude that while labor relations and welfare institutions constrained the trade policy choices made by labor unions in the United States and Europe, they do not tell the whole story. It would seem that United States labor unions were more sensitive to the potential risks for workers associated to the liberalization of trade than were their European counterparts.

Teachers' reactions on students' responses: essential for an adequate task monitoring

This research project analyzes the reactions the teacher has on students' responses. Different techniques as discourse markers, types of questions and repair sequences are taken into account, but the author puts a special emphasis on non-verbal communication. To be aware of all these ways of reacting in a class interaction is essential for an adequate task monitoring

Pd-catalysed amidation of 2,6-dihalopurine nucleosides. Replacement of iodine at 0 ºC

Pd-catalysed reactions of 2-Cl, 2-Br and 2-I derivatives of a 6-chloropurine nucleoside with benzamide have been compared, using Pd2dba3, Xantphos and Cs2CO3 in toluene, between 20 and 80 °C. The reactivity order was 2-I > 2-Br > 6-Cl ≫ 2-Cl. The 2-I substituent could be replaced even at 0 °C, under conditions disclosed here for the first time. On the other hand, the replacement of the chlorine atom at position 2 (2-Cl) required 110 °C.

LMS y web 2.0 una relación simbiótica en las aulas universitarias Diseño e integración de actividades pedagógicas 2.0 en una plataforma Blackboard

Peer-reviewed

LMS y web 2.0 una relación simbiótica en las aulas universitarias. Diseño e integración de actividades pedagógicas 2.0 en una plataforma Blackboard

Peer-reviewed

1,2-Dimethylindole-3-sulfonyl (MIS) as protecting group for the side chain of arginine

The protection of arginine (Arg) side chains is a crucial issue in peptide chemistry because of the propensity of the basic guanidinium group to produce side reactions. Currently, sulfonyl-type protecting groups, such as 2,2,5,7,8-pentamethylchroman (Pmc) and 2,2,4,6,7-pentamethyldihydrobenzofurane (Pbf), are the most widely used for this purpose. Nevertheless, Arg side chain protection remains problematic as a result of the acid stability of these two compounds. This issue is even more relevant in Arg-rich sequences, acid-sensitive peptides and large-scale syntheses. The 1,2-dimethylindole-3-sulfonyl (MIS) group is more acid-labile than Pmc and Pbf and can therefore be a better option for Arg side chain protection. In addition, MIS is compatible with tryptophan-containing peptides.

Complexes of Pd(II) and Pt(II) with 9-aminoacridine: reactions with DNA and study of their antiproliferative activity

Four new metal complexes {M = Pd(II) or Pt(II)} containing the ligand 9-aminoacridine (9AA) were prepared. The compounds were characterized by FT-IR and 1H, 13C, and 195Pt NMR spectroscopies. Crystal structure of the palladium complex of formulae [Pd(9AA)(μ-Cl)]2 · 2DMF was determined by X-ray diffraction. Two 9-acridine molecules in the imine form bind symmetrically to the metal ions in a bidentate fashion through the imine nitrogen atom and the C(1) atom of the aminoacridine closing a new five-membered ring. By reaction with phosphine or pyridine, the Cl bridges broke and compounds with general formulae [Pd(9AA)Cl(L)] (where L = PPh3 or py) were formed. A mononuclear complex of platinum of formulae [Pt(9AA)Cl(DMSO)] was also obtained by direct reaction of 9-aminoacridine and the complex [PtCl2(DMSO)2]. The capacity of the compounds to modify the secondary and tertiary structures of DNA was evaluated by means of circular dichroism and electrophoretic mobility. Both palladium and platinum compounds proved active in the modification of both the secondary and tertiary DNA structures. AFM images showed noticeable modifications of the morphology of the plasmid pBR322 DNA by the compounds probably due to the intercalation of the complexes between base pairs of the DNA molecule. Finally, the palladium complex was tested for antiproliferative activity against three different human tumor cell lines. The results suggest that the palladium complex of formula [Pd(9AA)(μ-Cl)]2 has significant antiproliferative activity, although it is less active than cisplatin.

Complexes of Pd(II) and Pt(II) with 9-aminoacridine: reactions with DNA and study of their antiproliferative activity

Four new metal complexes {M = Pd(II) or Pt(II)} containing the ligand 9-aminoacridine (9AA) were prepared. The compounds were characterized by FT-IR and 1H, 13C, and 195Pt NMR spectroscopies. Crystal structure of the palladium complex of formulae [Pd(9AA)(μ-Cl)]2 · 2DMF was determined by X-ray diffraction. Two 9-acridine molecules in the imine form bind symmetrically to the metal ions in a bidentate fashion through the imine nitrogen atom and the C(1) atom of the aminoacridine closing a new five-membered ring. By reaction with phosphine or pyridine, the Cl bridges broke and compounds with general formulae [Pd(9AA)Cl(L)] (where L = PPh3 or py) were formed. A mononuclear complex of platinum of formulae [Pt(9AA)Cl(DMSO)] was also obtained by direct reaction of 9-aminoacridine and the complex [PtCl2(DMSO)2]. The capacity of the compounds to modify the secondary and tertiary structures of DNA was evaluated by means of circular dichroism and electrophoretic mobility. Both palladium and platinum compounds proved active in the modification of both the secondary and tertiary DNA structures. AFM images showed noticeable modifications of the morphology of the plasmid pBR322 DNA by the compounds probably due to the intercalation of the complexes between base pairs of the DNA molecule. Finally, the palladium complex was tested for antiproliferative activity against three different human tumor cell lines. The results suggest that the palladium complex of formula [Pd(9AA)(μ-Cl)]2 has significant antiproliferative activity, although it is less active than cisplatin.

Complexes of Pd(II) and Pt(II) with 9-aminoacridine: reactions with DNA and study of their antiproliferative activity

Four new metal complexes {M = Pd(II) or Pt(II)} containing the ligand 9-aminoacridine (9AA) were prepared. The compounds were characterized by FT-IR and 1H, 13C, and 195Pt NMR spectroscopies. Crystal structure of the palladium complex of formulae [Pd(9AA)(μ-Cl)]2 · 2DMF was determined by X-ray diffraction. Two 9-acridine molecules in the imine form bind symmetrically to the metal ions in a bidentate fashion through the imine nitrogen atom and the C(1) atom of the aminoacridine closing a new five-membered ring. By reaction with phosphine or pyridine, the Cl bridges broke and compounds with general formulae [Pd(9AA)Cl(L)] (where L = PPh3 or py) were formed. A mononuclear complex of platinum of formulae [Pt(9AA)Cl(DMSO)] was also obtained by direct reaction of 9-aminoacridine and the complex [PtCl2(DMSO)2]. The capacity of the compounds to modify the secondary and tertiary structures of DNA was evaluated by means of circular dichroism and electrophoretic mobility. Both palladium and platinum compounds proved active in the modification of both the secondary and tertiary DNA structures. AFM images showed noticeable modifications of the morphology of the plasmid pBR322 DNA by the compounds probably due to the intercalation of the complexes between base pairs of the DNA molecule. Finally, the palladium complex was tested for antiproliferative activity against three different human tumor cell lines. The results suggest that the palladium complex of formula [Pd(9AA)(μ-Cl)]2 has significant antiproliferative activity, although it is less active than cisplatin.

Highly efficient, multigram and enantiopure synthesis of (S)-2-(2,4′-bithiazol-2-yl)pyrrolidine

(S)-2-(4-Bromo-2,4"-bithiazole)-1-(tert-butoxycarbonyl)pyrrolidine ((S)-1) was obtained as a single enantiomer and in high yield by means of a two-step modified Hantzsch thiazole synthesis reaction when bromoketone 3 and thioamide (S)-4 were used. Further conversion of (S)-1 into trimethyltin derivative (S)-2 broadens the scope for further cross-coupling reactions.

Pd-catalysed amidation of 2,6-dihalopurine nucleosides. Replacement of iodine at 0 ºC

Pd-catalysed reactions of 2-Cl, 2-Br and 2-I derivatives of a 6-chloropurine nucleoside with benzamide have been compared, using Pd2dba3, Xantphos and Cs2CO3 in toluene, between 20 and 80 °C. The reactivity order was 2-I > 2-Br > 6-Cl ≫ 2-Cl. The 2-I substituent could be replaced even at 0 °C, under conditions disclosed here for the first time. On the other hand, the replacement of the chlorine atom at position 2 (2-Cl) required 110 °C.