In order to study the influence of heterocyclic nuclei on the photochemical behavior of conjugated butadiene systems, novel butadiene derivatives E,Z‐ and ...E,E‐2/3‐4‐(2‐vinylphenyl)buta‐1,3‐dienylthiophene as well as E,Z‐ and E,E‐3/4‐4‐(2‐vinylphenyl)buta‐1,3‐dienylpyridine have been synthesized. The Wittig reaction was utilized in a two‐step reaction course. During the first Wittig reaction, the corresponding aldehydes, namely 2/3‐thiophenecarboxaldehyde and 3/4‐pyridinecarboxaldehyde, reacted with formylmethylenetriphenylphosphorane to give the corresponding acrylaldehydes, which reacted with the diphosphonium salt of α,α′‐o‐xylenedibromide in the second Wittig reaction to give new butadiene derivatives. These butadiene derivatives afforded, by photochemical intramolecular cycloaddition, new fused tricyclic as well as tetracyclic derivatives. For the first time, a study of efficiency was conducted where the efficiency of intramolecular cycloaddition of these heterocyclic butadiene derivatives was investigated by simultaneous use of ferrioxalate and valerophenone actinometers.
To study the influence of heterocyclic nuclei on the photochemical behavior of conjugated butadiene systems, novel butadiene derivatives have been synthesized by multiple use of the Wittig reaction. These butadiene derivatives afforded new fused tricyclic as well as tetracyclic products by photochemical intramolecular cycloaddition.
To study the effects of the position of the hexatrienyl moiety on the oxazole ring, novel substituted cis/trans‐2/4/5‐(2‐vinylstyryl)oxazoles have been synthesized. These novel compounds were ...prepared by Wittig reaction from the diphosphonium salt of α,α′‐o‐xylenedibromide, formaldehyde and the corresponding 2‐methyl‐4‐, 4‐methyl‐2‐, 2‐pheny‐5‐ and 4‐methyl‐5‐oxazolecarbaldehyde, respectively. Aldehydes were synthesized by using several synthetic approaches. By applying intramolecular photocycloaddition, 2‐methyl‐4‐(2‐vinylstyryl)oxazole afforded, as major product, fused oxazoline‐benzobicyclo3.2.1octene with small quantities of 4‐(1,2‐dihydronaphthalen‐2‐yl)‐2‐methyloxazole, as electrocyclization product. Upon irradiation of 4‐methyl‐5‐(2‐vinylstyryl)oxazole, endo‐ and exo‐benzobicyclo2.1.1hexene products were formed by 2+2 cycloaddition; this was the first instance of the 1,4‐closure to the bicyclo2.1.1hexene skeleton in the 2‐, 4‐, and 5‐oxazole‐stilbene derivatives studied so far. Derivatives 2‐phenyl‐5‐ and 4‐methyl‐2‐(2‐vinylstyryl)oxazole did not react and gave only high‐weight molecular products but were crucial as a comparison in the overall mechanistic study. We have found that, depending on the position of the hexatrienyl moiety in the oxazole ring, as well as on the position of the methyl/phenyl substituents, these new vinylstyryl‐2/4/5‐oxazole derivatives show diverse photochemical behavior.
To study the effects of the position of the hexatrienyl moiety on the oxazole ring, targeted substituted cis/trans‐2/4/5‐(2‐vinylstyryl)oxazoles have been synthesized and irradiated. These new vinylstyryl‐2/4/5‐oxazole derivatives showed diverse photochemical behavior and gave new functionalized oxazole and oxazoline polycyclic products.
Excited states of stilbenylpyrroles 1a − 1c deactivate by two photochemical processes: cis−trans-isomerization and hydrogen transfer of NH to the stilbene double bond. NH-transfer results in the ...formation of two quinone dimethane intermediates, 10 and 11, and biradicals 12. Intramolecular cyclization of intermediates 10 − 12 gives rise to polycyclic compounds spiro-2H-pyrroles 7, pyrroloisoindoles 3, and pyrroloisoquinolines 8. Spiro-2H-pyrroles 7 rearrange on silica gel, giving dihydroindoles 2.
Low density lipoprotein (LDL) particles exhibit extremely complex three-dimensional structural organization which is still not understood at the molecular level. The aim of this study was to provide ...the experimental evidence of a direct non-covalent interaction of the protein part with the lipid matrix. The approach was based on the combination of
1H NMR (600
MHz) spectroscopy with thiol-specific spin labeling of the protein (apoB). It is shown that the spectral peaks assigned to the methyl head groups of phosphatidylcholine and sphingomyelin in the
1H spectra of LDL exhibit line broadening when otherwise free thiol groups of apoB are covalently modified by methanethiosulfonate spin label. The effect is similar in the presence of water soluble paramagnetic compound. These results indicate that fragments of apoB, which are part of the receptor binding region, are directly in contact with the solvated phospholipid head groups of the lipid matrix.
