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Assignment of the 1H and 13C NMR spectra of 132(R)-methoxychlorophyll a using the two-dimensional HMQC and HMBC techniques

✍ Scribed by Ilkka Kilpeläinen; Seppo Kaltia; Pirjo Kuronen; Kristiina Hyvärinen; Paavo H. Hynninen

Publisher
John Wiley and Sons
Year
1994
Tongue
English
Weight
525 KB
Volume
32
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

The ^1^H and ^13^C NMR spectra of 13^2^(R)‐methoxychlorophyll a were assigned utilizing the two‐dimensional ^1^H‐detected heteronuclear one‐bond (HMQC) and multiple‐bond (HMBC) correlation techniques. The protons and carbons of the macrocycle and its short side‐chains could be completely assigned using the HMQC and HMBC data in concert. These techniques were also valuable in achieving assignments for the phytyl chain, which were previously incomplete. The proton and carbon assignments of the P1‐CH~2~, P2‐CH, P4‐CH~2~ and P15‐CH groups and those of all methyl groups of the phytyl chain could be established by the coupling patterns and by the combined information obtained from the HMQC and HMBC connectivities. Fairly unambiguous proton and carbon assignments were also obtained for the P6‐CH~2~, P7‐CH, P9‐CH~2~, P11‐CH and P14‐CH~2~ groups. The sensitivity of the HMQC and HMBC techniques is good, making it possible to achieve the spectral assignments under high dilution and monomeric conditions. This was considered to be of paramount importance in the structural analysis of chlorophylls and related compounds, which are difficult to prepare in adequate amounts and purity because of their lability and which show a strong aggregation tendency at higher concentrations and lower temperatures.

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