Substitution transformations naming

From our cmrent point of view we can say that each of two coordinate systems in which If has the form (19) are connected by the substitution (20). If we further demand that II has the invariant form (18) we must associate a special gauge transformation, namely... 

Examination of the pyrazino[2,3-rf]pyrimidine structure of pteridines reveals two principal pathways for the synthesis of this ring system, namely fusion of a pyrazine ring to a pyrimidine derivative, and annelation of a pyrimidine ring to a suitably substituted pyrazine derivative (equation 76). Since pyrimidines are more easily accessible the former pathway is of major importance. Less important methods include degradations of more complex substances and ring transformations of structurally related bicyclic nitrogen heterocycles. 

It can be assumed that the substrate 2-549 undergoes two elimination steps after lithiation to give 2-552 via 2-550 and 2-551. The last step is an intramolecular substitution affording 2-553, which was further transformed into the desired bioactive compound CMi-977 (also named LDP-977) (2-554). 

Systematic substitutive nomenclature may be used to name all organic molecules. However, those that are of animal or vegetable origin have often received trivial names, such as cholesterol, oxytocin and glucose. Biochemical nomenclature is based upon such trivial names, which are either substitutively modified in accordance with the principles, rules and conventions described in Chapter 4, Section 4.5 (p. 70), or transformed and simplified into names of stereoparent hydrides, i.e. parent hydrides of a specific stereochemistry. These names are then modified by the rules of substitutive nomenclature. Three classes of compound will be discussed here to illustrate the basic approach carbohydrates amino acids and peptides and lipids. For details, see Biochemical Nomenclature and Related Documents, 2nd Edition, Portland Press, London (1992). 

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