Control in Organisms

FIGURE 12.4 A simple molecule that acts as a plant hormone to promote maturation processes (ethylene) and a common animal hormone, testosterone, the male sex hormone. See Chapter 20, Section 20.3, for the meaning of line formulas, such as those shown for testosterone. 

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Double asymmetric synthesis and a new strategy for stereochemical control in organic synthesis [95]... 

Eysker, M. (2001). Strategies for internal parasite control in organic cattle , in Hovi, M. and Vaarst, M., Positive Health Preventive Measures and Alternative Strategies. Proceedings of the Fifth NAHWOA Workshop Rpdding, Denmark-November, 59-71. 

Speiser, B., Wyss, E. and Maurer, V. (2006). Biological control in organic production First choice or last option in Eilenberg, J. and Hokkanen, H. T. M. An Ecological and Societal Approach to Biological Control, Springer, Dordrecht, pp 27 46. 

Owing to the prohibition of chemosynthetic pesticides under organic farming standards, there is a greatly reduced availability of intervention/treatment-based methods for disease and pest control in organic fruit production systems. The efficacy of the permitted biological control, extract or mineral element (e.g. S and Cu)-based crop protection products is also usually lower than of chemosynthetic pesticides. Permitted plant protection products show efficacies of between 60 and 80% while chemosynthetic fungicides and pesticides often have efficacy levels >95% (Tamm et al., 2004). 

This chapter presents some examples of the asymmetric synthesis of complicated natural products. These examples will demonstrate that building up these molecules is unlikely if we do not use the asymmetric synthesis methodology. Excellent accounts by Masamune et al.1 and Noyori2 give a clear picture of the strategies for stereochemical control in organic synthesis. 

Ghorbani R, Wilcockson S, Leifert C (2006) Alternative treatments for late blight control in organic potato Antagonistic micro-organisms and compost extracts for activity against Phytophlhora infestans. Potato Res 48 171-179... 

Stacey DA (2003) Climate and biological control in organic crops. Int J Post Manage 49 205-214... 

Providing weed suppression through the use of allelopathic cover crops is an important method of weed control in organic farming and it is one of the best possibilities of allelopathy application (Sullivan 2003a). Besides, growing of cover... 

Brandsseter, L.O. and Riley, H. 2002. Cover crops and mulches for weed control in organically grown vegetables. In Cloutier, D.C. (ed.) Proceedings of the 5th EWRS Workshop on Physical and Cultural Weed Control. European Weed Research Society, Pisa. p. 174. 

Patriquin, D.G. 1988. Weed control in organic farming systems. In Altieri, M.A. and Liebman,... 

Rasmussen, LA., Askegaard, M. and Olesen, J.E. (1999). Weed control in organic crop rotations for grain production. In Gut, D. (ed.) Proceedings 11th EWRS Symposium. Basel, Switzerland. European Weed Research Society (EWRS), Wageningen. p. 98. 

In a subsequent publication, Corey and Sneen (125) mentioned that this "non-steric effect is stereochemical-electronic in nature" and on that basis introduced the term "stereoelectronic". This work (123-125) must therefore be considered one of the very first experimental and theoretical contributions to the principle of stereoelectronic control in organic chemistry. 

Masamune, S., Choy, W., Peterson, J.S., and Sita, L.R. (1985). Double asymmetric synthesis and a new strategy for stereochemical control in organic synthesis. Angewandte Chemie, International Edition in English, 24, 1-30. 

S. Masamune, W. Choy, J. S. Petersen, L. R. Sita, Double Asymmetric Synthesis and a New Strategy for Stereochemical Control in Organic Synthesis", Angew. Chem. Int. Ed. Engl. 1985, 24, 1-30. 

Review "Double Asymmetric Synthesis and a New Strategy for Stereochemical Control In Organic Synthesis"... 

The impact of weed control in organic production must not be underestimated. In vegetable production particularly, weed control will often pose more of a challenge than pest or disease control. It is the cost of controlling weeds that can have a significant effect on the economics of organic vegetable production. 

The dispersion and assembly behavior of silicon (Si) nanoclusters are controlled in organic and aqueous suspensions. Hydrogen-terminated Si nanoclusters are stably dispersed in non-polar solvents, but assemble on aqueous suspension surfaces. The nanoclusters spontaneously pack into lattice arrangements when a slow assembly rate is maintained. In addition, converting the nanocrystal surface to carboxylic acid termination stably disperses the nanocrystals in aqueous suspensions. They show size-dependent photoluminescence (PL) from yellow to green in the suspensions, while partly oxidizing the surface causes blue PL. 

Thermodynamic control in organic synthesis is very familiar, for example, in the synthesis of esters, acetals, or imines. Specific product formation can be favored by shifting the equilibrium position, through the removal or addition of water, the choice of solvent, the use of excess reagents, or by controlling the temperature and pressure of the reaction. Templates may be used in thermodynamically controlled synthesis to guide the system towards the production of a desired product that fits the template. 

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