Photolytic release of bioactive carboxylic acids from fused pyran conjugates

Abstract

 Coumarin (2H-benzopyran-2-one) derivatives with amino, phenyl, 4-methoxyphenyl and styryl groups at the 7-position, were synthesized and used in the derivatization of glycine and β-alanine.  The new ester cages of glycine and β-alanine, selected as models of carboxylic acid bioactive molecules, revealed to be interesting photo-responsive units.  A remarkable behaviour towards irradiation at higher wavelength (350 and 419 nm) occurred in conjugates obtained from 4-(chloromethyl)-7-styryl-2H-benzopyran-2one.  Time-resolved fluorescence studies complemented the photolysis results and proposed mechanism revealing the presence of different fluorescing species by the determination of decay associated spectra.  This study shows new promising alternative moieties for the development of photoactivable fluorescent acid prodrugs.

Dynamics of Excitons in Conjugated Molecules and Organic Semiconductor Systems

“…The photorepulsion of metal ions from a crown-ether-linked merocyanine was reported to occur very rapidly, on a picosecond time scale, because the stability constant of the complex in the excited state is about 2 orders of magnitude lower compared to that in the ground state; however, after deactivation of the excited state, the metal ion can reversibly be coordinated back. Photolytic release of bioactive carboxylic acids from fused pyran conjugates was demonstrated by Conceição et al, who showed that a correlation exists between the photolysis efficiency and the increasing extent of conjugation for both glycine and β-alanine …”

Visible-to-NIR-Light Activated Release: From Small Molecules to Nanomaterials

“…The introduction of a 7-NH 2 substituent ((7-aminocoumarin-4-yl)methyl, 30a ) 324 caused a ∼40–45 nm bathochromic shift of λ max abs ( Figure 3 ), and the liberation of carboxylic acids and amines from the corresponding esters and carbamates of 30a proceeded with Φ r values of 0.003–0.6 (λ irr = 350 or 419 nm). 308 , 324 , 339 , 340 Alkylation of the 7-amino moiety, which increases its electron-donating ability, resulted in a more red-shifted and intense absorption band in [7-(dimethylamino)coumarin-4-yl]methyl derivative 30b ( 290 , 334 , 341 ) and [7-(diethylamino)coumarin-4-yl]methyl analog 30c ( 301 , 334 ) ( Table 7 ). 278 , 290 , 301 The photorelease quantum yields for 30b and 30c exceeded those for all other compounds in this series.…”

“…However, detectable carboxylic acid release from these derivatives occurred only upon irradiation below 350 nm. 339 The introduction of a 7-styryl group 293 , 339 in 35a caused a more significant bathochromic shift of λ max abs that was further enhanced by substituting the para -position with EDGs ( 35b and 35c , Table 7 ; Figure 3 ). 293 The liberation of alcohols (caged through a carbonate linker) from 35c proceeded with Φ r = 8.3 × 10 –4 (λ irr = 420 nm), which is ∼50-times lower than the corresponding value for coumarin 30c (Φ r = 4.5 × 10 –2 ).…”

“…Gonçalves and co-workers expanded the coumarin π-system by substituting the 7-position with phenyl ( 34a ) or p -methoxy­phenyl ( 34b ) groups, resulting in bathochromic shifts in the absorption of 19 and 31 nm, respectively, relative to the parent coumarin 28a (Table ). However, detectable carboxylic acid release from these derivatives occurred only upon irradiation below 350 nm . The introduction of a 7-styryl group , in 35a caused a more significant bathochromic shift of λ max abs that was further enhanced by substituting the para -position with EDGs ( 35b and 35c , Table ; Figure ).…”