| Autor: |
McGrady, K A W, Overberger, C G |
| Zdroj: |
Polymer Journal; May 1987, Vol. 19 Issue: 5 p539-555, 17p |
| Abstrakt: |
The present report describes our current efforts to determine the nature of the cis/trans isomerization observed for poly(l-proline). Previously, we examined the effect that a substituent in the 5-position of the pyrrolidine ring had on the preferred conformations of poly(l-proline). We concluded that a bulkier group was needed in order to see significant changes in the conformation of polyproline. Thus, the synthesis of optically active poly(cis- and trans-5-isopropylproline) is described. The synthesis of the monomers involves the formation of ?'-2-isopropylpyrroline-5-carboxylic acid hydrochloride (III) which is prepared from the Michael adduct obtained from the reaction of 1-chloro-4-methyl-3-pentanone with diethylacetamidomalonate. Catalytic hydrogenation of III gives the hydrochloride salt of cis-5-isopropylproline. The trans isomer is obtained through a chemical separation method that depends on difference in reactivity between the cis and trans isomers to p-toluene sulfonyl chloride. The optical resolution of both isomers is carried out using fractional crystallization methods. Polymers of optically active cis- and trans-5-isopropylproline are obtained by ring-opening polymerization of the corresponding N-carboxyanhydrides. Low yields encountered in the polymerization of poly(cis-5-isopropylproline) can be attributed to instability of the N-carboxyanhydride. The possibility that ring conformation may be seriously altered by the presence of a large group in the 5-position is briefly considered. |
| Databáze: |
Supplemental Index |
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