- Chirality and biological activity:
- Limonene: S-limonene is responsible for the odor of lemon, and the R-limonene
for the odor of orange. - Carvone: S-carvone is responsible for the odor of spearmint (荷蘭薄荷), and the
R-carvone for the odor of caraway (香菜) seed. - Thalidomide: used to alleviate the symptoms of morning sickness in pregnant
women before 1963.
i) The S-enantiomer causes birth defect.
ii) Under physiological conditions, the two enantiomers are interconverted.
iii) Thalidomide is approved under highly strict regulations for treatment of a
serious complication associated with leprosy (麻瘋病).
iv) Thalidomide’s potential for use against other conditions including AIDS, brain
cancer, rheumatoid (風濕癥的) arthritis is under investigation.
- Limonene: S-limonene is responsible for the odor of lemon, and the R-limonene
- The origin of biological properties relating to chirality:
- The fact that the enantiomers of a compound do not smell the same suggests
that the receptor sites in the nose for these compounds are chiral, and only
the correct enantiomer will fit its particular site (just as a hand requires a glove
of the ocrrect chirality for a proper fit). - The binding specificity for a chiral molecule (like a hand) at a chiral receptor site
is only favorable in one way.
i) If either the molecule or the biological receptor site had the wrong handedness,
the natural physiological response (e.g. neural impulse, reaction catalyst) will
not occur. - Because of the tetrahedral stereocenter of the amino acid, three-point binding
can occur with proper alignment for only one of the two enantiomers.
- The fact that the enantiomers of a compound do not smell the same suggests
wang
(Wang)
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