A practical method for the synthesis of small peptides using DCC and HOBt as activators in HO-THF while avoiding the use of protecting groups.

The synthesis of peptides in solution proceeds through successive steps involving the removal of a protecting group and the formation of the peptide bond. While most methodological efforts have focused on the development of new protecting groups and coupling agents, methodologies based on minimal protecting groups have been less explored. In this research, a peptide synthesis methodology was developed using DCC and HOBt in THF-HO, avoiding the use of protecting groups, reducing reaction times, and reusing HOBt during successive couplings.

Solid acids as cocatalysts in the chelation-assisted hydroacylation of alkenes and alkynes.

The use of homogeneous Brønsted acid cocatalysts (such as benzoic acid) in hydroacylation reactions imine intermediates has been extensively studied. However, the use of heterogeneous cocatalysts has been limited to montmorillonite K10. Thus, we can use other solid acids to increase the efficiency of the reaction.

The Heck reaction of allylic alcohols catalysed by an N-heterocyclic carbene-Pd(ii) complex and toxicity of the ligand precursor for the marine benthic copepod .

The palladium-catalysed reaction of aryl halides and allylic alcohols is an attractive method for obtaining α,β-unsaturated aldehydes and ketones, which represent key intermediates in organic synthesis. In this context, a 1,2,3-triazol-5-ylidene (aNHC)-based palladium(ii) complex formed has been found to be a selective catalyst for the syntheses of building blocks from the corresponding aryl halides and allylic alcohols, with yields ranging from 50% to 90%. The lack of toxic effects of the ligand precursor (1,2,3-triazolium salt) of the palladium(ii) complex for the harpacticoid copepod allowed us to contrast the efficiency of the catalytic system with the potential impact of the principal waste chemical in global aquatic ecosystems, which has not been previously addressed.

In vitro efficacy of two terpenes against ancyrocephalid monogeneans from Nile tilapia.

Terpenes are naturally produced compounds with a broad range of biological activities. Currently, there is limited information regarding the anthelminthic effect of terpenes against monogenean parasites of fish. The aim of this work was to evaluate the in vitro efficacy of two terpenes [α-terpinene and (+)-limonene oxide] against ancyrocephalid monogeneans found on farmed Nile tilapia ().

A switchable [2]rotaxane asymmetric organocatalyst that utilizes an acyclic chiral secondary amine.

A rotaxane-based switchable asymmetric organocatalyst has been synthesized in which the change of the position of the macrocycle reveals or conceals an acyclic, yet still highly effective, chiral organocatalytic group. This allows control over both the rate and stereochemical outcome of a catalyzed asymmetric Michael addition.

Three new diarylbutane lignans from the resin of Bursera fagaroides.

Three new diarylbutane lignans, named 9-acetyl-9'-pentadecanoil-dihydroclusin (1), 2,3-demethoxy-secoisolintetralin monoacetate (4) and dihydroclusin monoacetate (5), have been isolated from the resin of Bursera fagaroides, together with two known ones, 2,3-demethoxy-secoisolintetralin diacetate (2) and dihydroclusin diacetate (3). The complete structure assignments were obtained by means of (1)H and (13)C NMR spectra.

Synthesis of azanucleosides through regioselective ring-opening of epoxides catalyzed by sulphated zirconia under microwave and solvent-free conditions.

New azanucleosides were obtained using sulphated zirconia (ZS) as catalyst in the nucleophilic oxirane ring opening reaction of 1-allyl-3-(oxiran-2-ylmethyl) pyrimidine-2,4(1H,3H)-dione and 1-allyl-5-methyl-3-(oxiran-2-ylmethyl)-pyrimidine-2,4(1H,3H)-dione, with (S)-prolinol. The new templates were obtained with good yields following a route which exploits the reactivity of epoxides in the presence of sulphated zirconia as catalyst. The key step was carried out using microwave and solvent-free conditions and proceeds with high selectivity.

Structure of salvioccidentalin, a diterpenoid with a rearranged neo-clerodane skeleton from Salvia occidentalis.

From the aerial parts of Salvia occidentalis (Labiatae) a new diterpenoid with a rearranged neo-clerodane skeleton was isolated. This new compound was named salvioccidentalin and its structure was established by spectroscopic means. A probable biogenetic relationship with salvigenolide from S.

A new languidulane diterpenoid from Salvia mexicana var. mexicana.

From the aerial parts of Salvia mexicana var. mexicana, two C-10 epimers (α and β) of salvimexicanolide were isolated. Our interpretation of the data, especially the 13C NMR, led us to conclude that the previously described 13C-NMR spectrum of the α-epimer was not accurately assigned and it actually corresponds to the β-epimer.

Oligomerization of 3,5-dimethyl benzyl alcohol promoted by clay: experimental and theoretical study.

Linear oligomerization of 3,5-dimethyl benzyl alcohol is induced by a montmorillonite clay (Tonsil Optimum Extra), producing 1,3,5,7-tetramethyl-9,10-dihydro-anthracene, which, by loss of protons results in the product 1,3,5,7-tetramethylanthracene. It was also found that the compounds 4-(3´,5´-dimethylbenzyl)-1,3,5,7-tetramethyl-9,10-dihydroanthracece and 4-(3´,5´-dimethylbenzyl)-1,3,5,7-tetra-methylanthracene were formed from 1,3,5,7-tetramethyl-9,10-dihydroanthracene. 1,3,5,7-Tetramethylanthryl radical cation was formed from 1,3,5,7-tetramethyl-9,10-dihydroanthracene; it was characterized by Electronic Paramagnetic Resonance (EPR).

Highly efficient macrolactonization of ω-hydroxy acids using benzotriazole esters: synthesis of Sansalvamide A.

A facile and mild macrolactonization reaction of ω-hydroxy acids was developed based on the transesterification of benzotriazole esters. Treatment of ω-hydroxy acids with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and 1-hydroxy benzotriazole (HOBT) in chloroform provided macrolactones in excellent yields. The reactions were performed under basic, neutral and acidic conditions using N,N-dimethylaminopyridine (DMAP), tetrabutylammonium tetrafluoroborate (TBABF(4)) and BF(3)·Et(2)O, respectively.

Homoisoflavanones from Agave tequilana Weber.

Three homoisoflavanones were isolated from the "piña" and leaves of Agave tequilana Weber. The compounds were identified as: 5,7-dihydroxy-3-(4-methoxybenzyl)-chroman-4-one (1), 7-hydroxy-3-(4-hydroxybenzyl)-chroman-4-one (2) and 4'-demethyl-3,9-dihydro-punctatin (3). This is the first phytochemical study carried out to Agave tequilana Weber.

Asymmetric sulfur ylide based enantioselective synthesis of D-erythro-sphingosine.

An asymmetric sulfur ylide reaction was employed to prepare an epoxide intermediate in a convergent manner. This epoxide was efficiently transformed into D-erythro-sphingosine.

Stannyl ceramides as efficient acceptors for synthesising beta-galactosyl ceramides.

beta-Galactosyl ceramides have been obtained in excellent yields and stereoselectivities by reacting disarmed glycosyl donors with stannyl ethers. The broad compatibility of stannyl ethers with various leaving group-promoter pairs is demonstrated.

Highly efficient and stereoselective synthesis of beta-glycolipids.

beta-Galactosylceramide and glycolipid analogues were prepared in high yield and with complete chemo and stereoselectivity by reaction of alpha-iodo glycosides with stannyl ceramides, formed in situ. TBAI was used to activate both the iodogalactose and the stannyl ether.

Recent advances in the glycosylation of sphingosines and ceramides.

Glycosphingolipids (GSLs) are ubiquitous components of eukaryotic cell membranes. They are highly bioactive and are involved in many aspects of cell signalling like cell-cell interaction, cell-substratum interaction and cell-pathogen interaction. GSLs also are involved in the modulation of signal transduction, resulting in regulation of cell proliferation and differentiation.