3147-18-0Relevant articles and documents
Steric Interaction Between the Peripheral Substituents of 10(S)-Chlorophyll Derivatives and its Conformational Consequences: a Proton Magnetic Resonance Study
Hynninen, Paavo H.,Loetjoenen, Simo
, p. 605 - 615 (1985)
The improved methods developed recently for the preparation of 10(S)-chlorophyll derivatives have permitted a detailed comparison of their conformations with those of the corresponding 10(R) derivatives, utilizing 1H NMR spectroscopy.Starting from the highly purified 10(S) derivative and following its conversion to the corresponding 10(R) form by repeated 1H NMR spectral measurements in acetone-d6, reliable values for the differences in the chemical shifts (Δδ) for each epimeric pair of compounds have been obtained.The relatively large Δδ values (0.1-0.2 ppm) observed for the P-1-CH2, P-H-2, P-3a-CH3 and 10b-CH3 signals were interpreted as indicating the proximity of the C-10 methoxycarbonyl group and the olefinic region of the phytyl group in the 10(S) derivatives.The proximity between these side-chains was considered to be derived principally from the three closely spaced carbonyls in the 10(S) derivatives.To minimize repulsion among the carbonyls, the C-7 and C-10 side-chains presumably assume conformations allowing maximal mutual distances for the carbonyls.As a compromise of various energetic factors, the phytyl group takes up a conformation where it bends to the right hand site of the macrocycle, or above rings V and III.This results in steric crowding between the olefinic region of the phytyl group and the C-10 methoxycarbonyl group.In addition, the other chemical shift increments show that the steric crowding between the bulky side-chains of the 10(S) derivatives increases the steric strain at the periphery of the macrocycle, relieved by pronounced conformational changes in rings IV and V and, to a lesser extent, also in the whole phorbin ring.The conformational differences were found to be larger for the magnesium-free epimers than for the chlorophylls.In the former case, they were also manifested by relatively large Δδ values (0.1-0.5 ppm) for the pyrrole NH protons.
Effects of molecular structures on reduction properties of formyl groups in chlorophylls and pheophytins prepared from oxygenic photosynthetic organisms
Sadaoka, Kana,Kashimura, Shigenori,Saga, Yoshitaka
, p. 3901 - 3905 (2011)
Reduction of the 7-formyl groups in chlorophyll (Chl) b and its demetalated compound pheophytin (Phe) b was kinetically analyzed by using tert-butylamine-borane complex (t-BuNH2·BH3), and was compared with that of the 3-formyl groups in Chl d and Phe d. Reduction kinetics of the 7-formyl group in Chl b was similar to that in Phe b in dichloromethane containing 5 mM t-BuNH2·BH3. Little difference of the reduction kinetics of the 7-formyl groups between Chl b and Phe b was in sharp contrast to the reduction kinetics of the 3-formyl groups in Chl d and Phe d: the 3-formyl group in Phe d was reduced 5.3-fold faster than that in Chl d. The 7-formyl groups in Chl b and Phe b were reduced more slowly than the 3-formyl groups in Chl d and Phe d, respectively. The difference of the reactivity between the 3- and 7-formyl groups was in line with 13C NMR measurements of chlorophyllous pigments, in which the chemical shifts of carbon atoms in the 7-formyl groups of Chl b and Phe b were high-field shifted compared with those in the 3-formyl groups of Chl d and Phe d, respectively. These indicate that the 7-formyl groups in chlorophyllous pigments were less reactive for reduction to the corresponding hydroxymethyl groups than the 3-formyl groups due to the difference in electronic states of the formyl groups in the A- and B-rings of the chlorin macrocycle.
Preparation of Chlorophylls and Pheophytins by Isocratic Liquid Chromatography
Watanabe, Tadashi,Hongu, Akinori,Honda, Kenichi,Nakazato, Masataka,Konno, Mitsuo,Saitoh, Sadao
, p. 251 - 256 (2007/10/02)
Isocratic high-performance liquid chromatography (HPLC) with silica gel as a stationary phase provides a powerful means for rapid preparative isolation (on a 20-50 mg level) of chlorophylls (a, a', b, and b') and pheophytins (a, a', b, and b').The purity and identity of the isolated pigments have been confirmed by complete elemental analyses and analytical HPLC; the purity levels were 99.9, 99.5, 99.5, 99.4, 95, 91, 99.5, and 85percent for chlorophyll a, a', b, and b' and pheophytin a, a', b, and b', respectively, with the sole impurities being almost totally the corresponding epimers.UV-visible spectrometric data (in diethyl ether, acetone, and benzene) and CD spectra (in benzene) of the purified pigments are presented.
