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A strategy based on the diastereoselective dipolar cycloaddition reaction of nitrile oxides and allylic alcoholates, has been applied to the synthesis of bis-(isoxazolines) that are precursors to polyketide fragments. These intermediates can be elaborated into protected polyols, for example, 439, by sequential chemos-elective reductive opening of each isoxazoline or, alternatively, by simultaneously, providing access to all stereoisomers of this carbon skeleton (479). 

Recent advances in the rhodium-catalyzed [4-1-2] reactions have led to the development of the first highly regioselective intermolecular cyclization, providing access to new classes of carbocycles with both activated and unactivated substrates. The chemo- and stereoselective carbocyclizations of tethered diene-allene derivatives afford new classes of 5,6- and 6,6-bicyclic systems. Additionally, examination of a wide range of factors that influence both diastereo- and enantioselectivity has provided a significant advance in the understanding of catalyst requirements across these systems. 

Habib-Zahmani H, Hacini S, Charormet E, Rodriguez J (2002) A new multicomponent domino transformation of 1,3-dicarbonyl compounds one-pot regio-, chemo- and stereoselective access to valuable alpha,gamma-difunctionalized alpha-ketoesters and amides. Synlett 1827-1830... 

Chemoenzymatic polymerizations have the potential to further increase macro-molecular complexity by overcoming these limitations. Their combination with other polymerization techniques can give access to such structures. Depending on the mutual compatibility, multistep reactions as well as cascade reactions have been reported for the synthesis of polymer architectures and will be reviewed in the first part of this article. A unique feature of enzymes is their selectivity, such as regio-, chemo-, and in particular enantioselectivity. This offers oppormnities to synthesize novel chiral polymers and polymer architectures when combined with chemical catalysis. This will be discussed in the second part of this article. Generally, we will focus on the developments of the last 5-8 years. Unless otherwise noted, the term enzyme or lipase in this chapter refers to Candida antarctica Lipase B (CALB) or Novozym 435 (CALB immobilized on macroporous resin). 

An alternative method for the preparation of a kinetic zinc ketone enolate (123) from an arene thiol ester 121 and bis(iodozincio)methane (122) in the presence of a palladium(O) catalyst was developed by Matsubara and coworkers (equation 36) . The modest reactivity of the zinc reagent 122 makes this transformation highly chemo- and regioselective neither isomerization of the kinetic enolate 123 nor a palladium-catalyzed coupling with the thiol ester 121 could be observed. Thus, treatment of zinc enolate 123 with various aldehydes or ketones led regioselectively to one aldol product 124. The method provides access to reactive functionalized zinc enolates which are otherwise hard to obtain. 

Childers S. E., Ciufo S., and Lovley D. R. (2002) Geobacter metallireducens accesses insoluble Fe(III) oxide by chemo-taxis. Nature 416, 767-769. 

Up-regulation. The occasional exacerbation of ischaemic cardiac disease on sudden withdrawal of a p-adrenoceptor blocker may be explained by up-regulation during its administration, so that on withdrawal, an above-normal number of receptors suddenly becomes accessible to the normal chemo-transmitter, i.e. noradrenaline (norepinephrine). 

Nucleophilic attack of the central carbon of allyl ligands represents an important access to metallacyclobutanes independent from cyclopropanes as precursors. This reaction pathway competes with the more common attack at one of the terminal allylic carbons. However, several examples of metallacyclobutane formation followed by release of cyclopropane products have been reported, especially with allyl complexes of palladium, platinum, and iridium as stable precursors or reactive intermediates in catalytic cycles. Detailed experimental (see below) and theoretical studies considering chemo-, regio- and stereoselectivity of the crucial reaction steps with respect to influence of the metal, ligands, substituents and reaction conditions are available. ... 

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