Resolution of the alpha-beta-dihydroxy-alpha-methyl-beta-isopropyladipic acids / by T.A. Henry and H. Paget.
- Thomas Anderson Henry
- Date:
- [1923.]
Licence: Public Domain Mark
Credit: Resolution of the alpha-beta-dihydroxy-alpha-methyl-beta-isopropyladipic acids / by T.A. Henry and H. Paget. Source: Wellcome Collection.
5/16 page 1880
![As Wallach had already synthesised the acid melting at 189° (Annalen, 1908, 362, 268) from dimethylacetonylacetone, his experiments were repeated, and yielded not one but all three inactive acids, the relative amounts obtained being acid of m. p. 203—204°; acid of m. p. 189°; acid of m. p. 198° = 3:1:1. There can be no doubt that the acid melting at 189° is a chemical individual, since it crystallises quite differently from the other two forms, is more soluble than either, and is separable from either by crystallisation. Further, it can be prepared by dissolving the other two forms in hot wTater, allowing whichever form is in excess to crystallise out, and then concentrating the liquid until crystallisation again begins, when the form, m. p. 189°, invariably separates. A similar form of aa-dimethylglutaric acid, C02H*CHMe*[CH2]3*CHMe*C02H, m. p. 105—107°, was described by Bone and Perkin (T., 1896, 69, 268), which, though not separable into its components by fractional crystallisation from any solvent, could be separated into the ordinary trans- and cZ<s-forms by crystallisation of the calcium hydrogen salt (compare Auwers, Ber., 1895, 28, 263), or by warming with acetyl chloride, when the cbs-form readily yielded an anhydride, whilst the Zra.as-form remained unchanged. It seems clear in view of their physical properties and the differ¬ ence in their modes of losing water that the acid of m. p. 203—204° is the a^Zi-form, and the acid of m. p. 198° the para-form, whilst the third acid, m. p. 189°, is a combination of these two. Unlike most of the similar acids in this series, no evidence has been found of interconversion between the anti- and para-forms. The anti and para-acids have both been resolved into their optically active forms, the former by fractional crystallisation of the quinine and cinchonine salts, the second alkaloid being the more convenient agent, and the latter by the use of quinine. The principal facts regarding the two pairs of optically active forms and their salts are summarised in the table opposite. It will be seen from this table that in the case of the anti-acid, Z-quinine and cZ-cinchonine both separate the dextro-form of the acid first, whilst cZ-quinidine effects virtually no separation, the salts with the d- and Z-forms of the acid being about equally soluble. In the case of the quinine salt, there appears to be no change in the sign of rotation, the salt with the d-acid being, as is to be expected, of lower rotation than that of the salt with the Z-acid. W ith quinidine, on the contrary, such a change does occur, the salt with the Z-acid having a higher rotation than that with the cZ-acid. In the case of cinchonine no comparison can be made, as the salt with the Z-acid is abnormal in composition.](https://iiif.wellcomecollection.org/image/b30624058_0005.jp2/full/800%2C/0/default.jpg)
