Developing synthetic methods for bioactive phosphorus compounds using H-phosphonate chemistry: a progress report

In this paper a short account of our recent research concerning the development of new synthetic methods and reagents for the preparation of nucleotides and their analogues, is given.     

Solid phase synthesis of oligoribonucleotides using the o-nitrobenzyl group for 2''-hydroxyl protection and H-phosphonate chemistry.

Oligoribonucleotides with chain length of 7, 11, 15, 17, 24 and 34 were synthesized on long chain alkylamine controlled pore glass beads (LCA-CPG) using o-nitrobenzyl protection of 2'-hydroxyls via a H-phosphonate approach either manually or by using an automatic synthesizer. The oligoribonucleotides were obtained in yields of 0.6 0.6-20%, based on initial nucleoside bound to the LCA-CPG support.     

5-Substituted-1H-tetrazoles as carboxylic acid isosteres: medicinal chemistry and synthetic methods

5-Substituted-1H-tetrazoles (RCN4H) are often used as metabolism-resistant isosteric replacements for carboxylic acids (RCO2H) in SAR-driven medicinal chemistry analogue syntheses. This review provides a brief summary of the medicinal chemistry of tetrazolic acids and highlights some examples of tetrazole-containing drug substances in the current literature. A survey of representative literature procedures for the preparation of 5-substituted-1H-tetrazoles, focusing on preparations from aryl and alkyl nitriles, is presented in sections by generalized synthetic methods.     

Lichens as a potential natural source of bioactive compounds: a review

Biological activity of material whether known in folk medicine or observed in planned screening program has been the starting point in the drug research. The general pattern is the isolation of active principles, elucidation their structures, followed by attempts for modulation of its activity potential by chemical modification. Lichens are valuable plant resources and are used as medicine, food, fodder, perfume, spice, dyes and for miscellaneous purposes throughout the world. Lichens are well known for the diversity of secondary metabolites that they produce. Compounds isolated from various lichen species have been reported to display diverse biological activities. Here we review the medicinal efficacy of lichen substances, which intends to explore the pharmaceutical potential of lichen substances.     

Assessment of synthetic methods for the preparation of N-beta-d-glucopyranosyl-N'-substituted ureas, -thioureas and related compounds

Preparation of O-peracetylated N-beta-d-glucopyranosyl-N'-acyl urea derivatives resulted in the formation of anomeric mixtures under the following conditions: acylation of O-peracetylated beta-d-glucopyranosyl urea by acyl chlorides in the presence of ZnCl(2) in refluxing CHCl(3); addition of O-peracetylated beta-d-glucopyranosylamine to acyl isocyanates in acetonitrile at rt; addition of carboxamides to in situ prepared O-peracetylated beta-d-glucopyranosyl isocyanate in refluxing toluene. Deprotection of O-peracetylated N-beta-d-glucopyranosyl-N'-acyl ureas either under base (NaOMe in MeOH at or below rt) or under acid (KHSO(4) or AcCl in MeOH at rt) catalyzed transesterification conditions resulted in unavoidable partial cleavage of the N'-acyl moieties. Reaction of beta-d-glucopyranosylammonium carbamate with an isocyanate, isothiocyanate or isoselenocyanate in dry pyridine at rt appears as a general method for the preparation of the corresponding beta-d-glucopyranosyl ureas, -thio- and -selenoureas, respectively, inclusive N'-acyl derivatives.     

Developing strategies and methods for rehabilitating degraded pastures using native grasses

Summary   The purpose of this comment paper is to highlight the need for more research that aims to develop strategies and methods for establishing and maintaining native grasses in degraded pastures. Clues to finding the best strategies are linked to the vigorous debate concerning the relationship between biodiversity and ecosystem function, which has resonated in ecological research for more than 20 years. Studies aimed at investigating the operational validity of the 'sampling effect' hypothesis vs. the 'niche complementarity' hypothesis could provide valuable direction on how to successfully re-establish healthy and stable native pasture communities, including the number of species and functional groups needed. Once strategies have been developed, then practical methods on grazing management and sowing are also needed. In the long run, research initiatives in this direction could act to benefit the conservation of native grass diversity, while at the same time, sustain important ecological (and economic) functions such as production, nutrient cycling and resistance to invasion.     

Managing agricultural phosphorus for water quality protection: principles for progress

Background

The eutrophication of aquatic systems due to diffuse pollution of agricultural phosphorus (P) is a local, even regional, water quality problem that can be found world-wide.

Scope

Sustainable management of P requires prudent tempering of agronomic practices, recognizing that additional steps are often required to reduce the downstream impacts of most production systems.

Conclusions

Strategies to mitigate diffuse losses of P must consider chronic (edaphic) and acute, temporary (fertilizer, manure, vegetation) sources. Even then, hydrology can readily convert modest sources into significant loads, including via subsurface pathways. Systemic drivers, particularly P surpluses that result in long-term over-application of P to soils, are the most recalcitrant causes of diffuse P loss. Even in systems where P application is in balance with withdrawal, diffuse pollution can be exacerbated by management systems that promote accumulation of P within the effective layer of effective interaction between soils and runoff water. Indeed, conventional conservation practices aimed at controlling soil erosion must be evaluated in light of their ability to exacerbate dissolved P pollution. Understanding the opportunities and limitations of P management strategies is essential to ensure that water quality expectations are realistic and that our beneficial management practices are both efficient and effective.     

Using synthetic chemistry to understand copper protein active sites: a personal perspective

The results of studies performed in the author’s laboratory are surveyed, with particular emphasis on demonstrating the value of a multidisciplinary synthetic modeling approach for discovering new and unusual chemistry helpful for understanding the properties of the active sites of copper proteins or assessing the feasibility of mechanistic pathways they might follow during catalysis. The discussion focuses on the progress made to date toward comprehending the nitrite reductase catalytic site and mechanism, the electronic structures of copper thiolate electron transfer centers, the sulfido-bridged “Cu_Z” site in nitrous oxide reductase, and the processes of dioxygen binding and activation by mono- and dicopper centers in oxidases and oxygenases.     

Yeast cells for encapsulation of bioactive compounds in food products: A review

Nowadays bioactive compounds have gained great attention in food and drug industries owing to their health aspects as well as antimicrobial and antioxidant attributes. Nevertheless, their bioavailability, bioactivity, and stability can be affected in different conditions and during storage. In addition, some bioactive compounds have undesirable flavor that restrict their application especially at high dosage in food products. Therefore, food industry needs to find novel techniques to overcome these problems. Microencapsulation is a technique, which can fulfill the mentioned requirements. Also, there are many wall materials for use in encapsulation procedure such as proteins, carbohydrates, lipids, and various kinds of polymers. The utilization of food-grade and safe carriers have attracted great interest for encapsulation of food ingredients. Yeast cells are known as a novel carrier for microencapsulation of bioactive compounds with benefits such as controlled release, protection of core substances without a significant effect on sensory properties of food products. Saccharomyces cerevisiae was abundantly used as a suitable carrier for food ingredients. Whole cells as well as cell particles like cell wall and plasma membrane can act as a wall material in encapsulation process. Compared to other wall materials, yeast cells are biodegradable, have better protection for bioactive compounds and the process of microencapsulation by them is relatively simple. The encapsulation efficiency can be improved by applying some pretreatments of yeast cells. In this article, the potential application of yeast cells as an encapsulating material for encapsulation of bioactive compounds is reviewed.