Stereochemical definitions

A Macromolecular Division of lUPAC was created in 1967, and it created a permanent Commission on Macromolecular Nomenclature, parallel to the other nomenclature commissions. The Commission over the years has issued recommendations on basic definitions, stereochemical definitions and notations, stmcture-based nomenclature for regular single-strand organic polymers and regular single-strand and quasisingle-strand inorganic and coordination polymers, source-based nomenclature for copolymers, and abbreviations for polymers. AH of these are coUected in a compendium referred to as the lUPAC Purple Book (99). 

Basie definitions of terms relating to polymerization reactions [1,2] and stereochemical definitions and notations relating to polymers [3] have been published, but no reference was made explieitly to reaetions involving the asymmetric synthesis of polymers. It is the aim of the present doeument to recommend classification and definitions relating to asymmetrie polymerizations that may produce optically active polymers. 

Stereochemical definitions and notations relating to polymers (Provisional), Pure Appl. Chem. 51, 1101-1121 (1979). Superseded by Ref 14. 

Until very recently apomorphine (APO) was the only important chiral DA agonist whose enantiomers had been studied. The only congeneric groups of resolved agonists to be reported subsequently were 2-aminotetralins 1, 2 ). The present enantiomer study of the SK F 38393 series thus provides welcome new data for stereochemical definition of DA receptors. Moreover, the previous studies employed rather narrow choices of pharmacological models. The broader range of models presented here is therefore particularly helpful. 

According to the classical stereochemical definition, the term conformation describes the different spatial arrangements of atoms in molecules that result solely from torsions (rotations) around single and/or partial double bonds. However in the domain of supramole-cular chemistry, molecular motions arise from the competitive noncovalent interactions between the components. 

Brandrup, J. Stereochemical Definitions and Notations Relating to Polymers, in Polymer Handbook, Wiley-Interscience, John Wiley Sons, New York, 1989, pp. 1/43-61. 

Stereochemical Definition and Notations Relating to Polymers (Recommendations 1980). Pure Appl. Chem., 53 (1981) 733. 

Cyclobutanes may be converted to alkenes thermally, the reverse of the [2 + 2] cycloaddition reaction. These retroaddition or cycloreversion reactions have important synthetic applications and offer further insights into the chemical behavior of the 1,4-diradical intermediates involved they may proceed to product alkenes or collapse to starting material with loss of stereochemistry. Both observations are readily accommodated by the diradical mechanism. Generation of 1,4-tetramethylene diradicals in other ways, such as from cyclic diazo precursors, results in formation of both alkenes and cyclobutanes, with stereochemical details consistent with kinetically competitive bond rotations before the diradical gives cyclobutanes or alkenes. From the tetraalkyl-substituted systems (5) and (6), cyclobutane products are formed with very high retention stereospecificity,while the diradicals generated from the azo precursors (7) and (8) lead to alkene and cyclobutane products with some loss of stereochemical definition. ... 

Cohen, F., Overman, L. E. Enantioselective total synthesis of batzelladine F structural revision and stereochemical definition. J. Am. Chem. Soc. 2001, 123, 10782-10783. 

Recently, the stereochemical definitions of the addition of carbenes to C-C double bonds have been summarized. The term stereoselectivity refers to the degree of selectivity for the formation of cyclopropane products having endo vs. exo or, alternatively, syn vs. anti orientation of the substituents in the carbene species relative to substituents in the alkene substrate. The term stereospecificity refers to the stereochemistry of vicinal cyclopropane substituents originating as double-bond substituents in the starting alkene, i.e. a cyclopropane-forming reaction is stereospecific if the cisjtrans relationship of the double-bond substituents is retained in the cyclopropane product. Diastereofacial selectivity refers to the face of the alkene to which addition occurs relative to other substituents in the alkene substrate. Finally, enantioselectivity refers to the formation of a specific enantiomer of the cyclopropane product. 

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