Stereo Formulas

Hudson, C. S., Historical Aspects of Emil Fischer s Fundamental Conventions for Writing Stereo-formulas in a Plane, III, 1-22... 

Some exercises follow in which you will work out R,S configurations from projection or stereo formulas and vice versa. If you have difficulty with these, we recommend you use the procedure of Figures 5-12 and 5-13 to translate projection formulas to or from ball-and-stick models, which then can be oriented, as in Figure 19-6, to determine, or to produce, particular R or S configurations. 

Exercise 19-9 Designate the configuration at each asymmetric carbon in each of the following projection or stereo formulas by both the d,l and fl.S systems ... 

It has become general practice to write the stereo-formulas for the anomeric forms of methyl D-glucopyranoside as I and II, and also to employ the alternative formulas la and Ila or Ib and Ilb. Through established conventions and definitions these stereo-formulas that are written in a plane, and independently also the assigned systematic... 

In historical accuracy, it should be remembered that Fischer s original second convention was applied to the enantiomorphous saccharic acids as the reference substances or standards his formula for natural glucose (XV) followed as a sequel. It has now become customary to select the enantiomorphous forms of glyceraldehyde as the reference substances or "standards, from the stereo-formulas of which there follow... 

The preceding formulas VII and XI to XVI have been written purposely without the use of d and I symbols for distinguishing the members of a pair of enantiomorphs in order to emphasize that the mechanical models and Fischer s conventional formulas for representing them are quite independent of any plan of nomenclature. Recognizing this independence, let us consider next the historical origin and development of systematic nomenclature for such models and stereo-formulas in the carbohydrate group. 

Hantzsch Stereo Formula.—A development of the Kekule formula to agree with the existence of isomeric diazotates was suggested by Hantzsch. He assumed geometric stereo-isomerism due to the double linking of two nitrogen atoms, and this assumption has been supported not only by the isomerism of the diazotates, but also of other similar... 

New proaporphine alkaloids are (-l-)-isocrotsparinine (1), (-I-)-N-methyliso-crotsparinine (2), and ( )-tetrahydroglaziovine (3), all obtained from Croton spar-siflorus. The stereochemistry of crotsparinine has been defined as in structure (4). Jacularine and Base-E, two minor alkaloids previously isolated from C. linearis have been assigned stereo formulas, with the former being enantiomeric with (1), and the latter being represented by (5)/... 

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