Structure and Conformation of Photosynthetic Pigments and Related Compounds. 10. Comparison of a Phytochlorin and Phytoporphyrin Derived from Chlorophyll<i>a</i>

Senge, Ma­thias O.; Smith, Kevin M.

doi:10.1107/s0108270197003648

Cited by 7 publications

(2 citation statements)

References 2 publications

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“…111°) were wider than those in the A- and C-rings (ca. 106°), meaning that the two inner hydrogen atoms were located on the nitrogen atoms in the B- and D-rings . In tautomer 1b , the β−β‘ double bonds on the A- and C-rings were relatively excluded from the 22π-system and were more reactive, which was consistent with the present regioselective dihydroxylation.…”

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confidence: 83%

Regioselective Transformation of Octaethylporphyrin into a Phytoporphyrin Analogue

2007

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An octaethylporphyrin derivative, 1, possessing an exo-five-membered ring fused at the 13- and 15-positions was oxidized by osmium tetroxide to give two isomeric chlorins, 3 and 5, possessing beta,beta'-dihydroxy groups at the A- and C-rings, respectively. Single dehydration of 2,3-dihydroxychlorin 3 gave a mixture of 2- and 3-(1-hydroxyethyl)porphyrins 7, while that of 12,13-dihydroxychlorin 5 resulted in the sole formation of 131-hydroxyporphyrin 9. The latter was modified smoothly to the phytoporphyrin analogue 2, whose molecular skeleton was similar to that of naturally occurring chlorophylls possessing a 131-oxo group fixed on an exo-five-membered ring.

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supporting

confidence: 83%

Regioselective Transformation of Octaethylporphyrin into a Phytoporphyrin Analogue

2007

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“…Crystal Structure Determination. The techniques and programs used for crystallographic studies are similar to those reported by Senge and Smith . Benzochlorin 8 , C 37 H 38 N 4 O 3 , at 130 K (Cu Kα radiation, λ = 1.54178 Å, 2 q max = 114°), monoclinic, space group P 2 1 , a = 13.384(7), b = 15.494(5), c = 15.840(6) Å, b = 114.41(4) o , V = 2991(2), Å 3 , Z = 4, two crystallographically independent molecules refined against [ F 2 ], 4135 independent reflections, 634 parameters, R 1 = 0.0699 { I > 2 σ ( I ), RI = 0.1135 (all data), wR 2 = 0.1975 (all data).…”

Section: Methodsmentioning

confidence: 98%

Synthesis and Spectroscopic Properties of Novel Benzochlorins Derived from Chlorophyll a

et al. 1998

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Methylpheophorbide-a (a chlorophyll a analog) was converted into methyl 131-deoxypyropheophorbide-a 2 in excellent yield. The Ni(II) complex of 2 on hydrogenation and subsequent Vilsmeier reaction with phosphorus oxychloride and 3-(N,N-dimethylamino)acrolein produced Ni(II) methyl 20-(2-formylvinyl)-131-deoxypyropheophorbide-a 4. In contrast to other synthetic and naturally occurring isobacteriochlorins, the isobacteriochlorin obtained by acid-catalyzed cyclization of 4 was found to be unstable and oxidized to the corresponding benzochlorin. The free base benzochlorin 7, obtained by demetalation, up on DDQ/methanol treatment produced a mixture of 132-oxo- and 131-methoxy-132-oxobenzochlorins 8, 9. Surprisingly, under similar reaction conditions, an ethanolic solution of DDQ afforded 131,132-dioxobenzochlorin 13 as a major product. Vilsmeier reaction (POCl3/DMF) of Ni(II) benzochlorin 6 gave unexpected 5-formyl-132-oxobenzochlorin 15. Zn(II) complexes of the newly synthesized benzochlorins showed long wavelength absorptions in the range of 750−753 nm. Thus, compared to the respective free base analogues bathochromic shifts of 40−42 nm were observed. Despite extensive studies in benzochlorins, these are the first examples which exhibit such remarkable long wavelength absorptions in their electronic absorption spectra. The structures of novel benzochlorins were confirmed by extensive NMR [2D NMR (ROESY), 13C NMR] and X-ray crystallographic studies. On the basis of the crystal structure of oxobenzochlorin 8, the chemical reactivity of other benzochlorin analogues were examined by semiempirical molecular orbital theory. Our results are in agreement with the previous qualitative electron sextet hypothesis proposed for chlorin systems by Woodward. The fluorescence quantum yields and the singlet oxygen yields of the free base and Zn(II) benzochlorins were measured relative to tetraphenylporphyrin (TPP) in benzene.

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Exercises in molecular gymnastics—bending, stretching and twisting porphyrins

2006

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The functional versatility of tetrapyrroles as natural cofactors is related to their conformational flexibility where manipulation of the macrocycle conformation allows a fine-tuning of their physicochemical properties. This feature article gives a personal account of the synthesis and solid state structural characterization of highly substituted, non-planar porphyrins. Their conformational analysis identifies sterically strained tetrapyrroles as a versatile class of biomimetic compounds with tailor-made properties.

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Structure and Conformation of Photosynthetic Pigments and Related Compounds. 10. Comparison of a Phytochlorin and Phytoporphyrin Derived from Chlorophylla

Cited by 7 publications

References 2 publications

Regioselective Transformation of Octaethylporphyrin into a Phytoporphyrin Analogue

Regioselective Transformation of Octaethylporphyrin into a Phytoporphyrin Analogue

Synthesis and Spectroscopic Properties of Novel Benzochlorins Derived from Chlorophyll a

Exercises in molecular gymnastics—bending, stretching and twisting porphyrins

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