Bicyclooctane-2-carboxylic Acid

The requirements for secondary sources are the same as those given previously for the reference set with the exception of the requirement that the set permit the o/ constants to be properly scaled. The p/iTaS of bicyclooctane carboxylic acids and of quinuclidines meet these requirements fairly well. The data available in the literature does not permit the evaluation of o/ for many additional substituents. The greatest potential source of additional aj values consists of >Ka values of acetic acids. To use the acetic acid system as a secondary source for the evaluation of U/ constants it must be shown that steric effects and resonance effects are absent. To establish that this is indeed the case, pAToS of substituted acids in water at 25° were correlated with the extended Hammett equation (Eq. 19) using primary (7/ constants (Table 7) obtained from Equation 58 and an constants obtained from Equation 40. Only those substituents for... 

As suggested by Roberts and Moreland many years ago (1953), the acidity constants of 4-substituted bicyclooctane-l-carboxylic acids provide a very suitable system for defining a field/induction parameter. In this rigid system the substituent X is held firmly in place and there is little possibility for mesomeric delocalization or polarization interactions between X and COOH (or COO-). Therefore, it can be assumed that X influences the deprotonation of COOH only through space (the field effect) and through intervening o-bonds. On this basis Taft (1956, p. 595) and Swain and Lupton (1968) were able to calculate values for o and crR. 

An example of a compound having a preferred boat conformation is that of [2.2.2] bicyclooctane. This compound must necessarily exist as a boat because its cis-4 hydroxy cyclohexane-carboxylic acid easily forms lactose and the water elimination must proceed through the boat conformation. The trans isomer will not lactonize. 

In Charton s work pKa data for 4-X-substituted-bicyclo[2.2.2.]octane-l-carboxylic acids in 50% w/w EtOH-H20 are the basis for primary molecular skeleton, the substituent is somewhat remote from the acidic centre and the geometry for 4-X and 1-COOH closely resembles that for groups in a 1,4-disubstituted benzene)81. However, the pKa value for the vinyl-substituted acid in this solvent was not available, so the 07 value for the vinyl group was calculated by substituting the pKa value for vinylacetic acid in water at 25 °C (4.352) in the regression equation 10 ... 

The Dewar-Golden-Harris (24/) treatment of substituent effects bases its localized effect parameters, F, on the ionization constants of 4-substituted bicyclo[2.2.2]octane-l-carboxylic acids. Thus, for bicyclooctane acids. 

Tropane alkaloids comprise a large group of bases occurring predominantly in the family of the Solanaceae. Structurally they are esters of carboxylic acids with tropine (3-hydroxy-8-aza-8-methyl-[3.2.1]-bicyclooctane) and are biosynthetically derived from amino acid and acetate precursors. Despite the relative structural simplicity of the alkaloids, their biosynthesis is not well understood from a mechanistic point of view. In this article the available information pertaining to this question is summarized and discussed in context with the information that is available from the analogous pelletierine class of alkaloids. A new proposal for the mechanism of assembly of the acetate derived C, fragment of these alkaloids is introduced. 

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