A new fluorescent-cholesterol (Cum-Chl) molecule has been synthesized by attaching 3-acetyl-7-(diethylamino)-2H-chromen-2-one (Cum) to cholesterol via cholesterol bound β-keto ester. The β-keto ester was synthesized from the corresponding nitrile by applying the Blaise reaction. The molecule forms H-aggregates in solutions. The efficiency of aggregation is high in water. The H-aggregates are non-fluorescent in non-aqueous solvents but fluorescent in water. Aqueous bile salt media suppress the formation of H-aggregates, this effect being more pronounced for sodium deoxycholate (NaDC) which is more hydrophobic. With increasing bile salt concentration, the enhancement of monomeric fluorescence intensity of Cum-Chl generally follows the progressive miceller aggregation of bile salts. Incorporation of Cum-Chl into the dimyristoylphosphatidylcholine (DMPC) lipid bilayer membrane results in a significant enhancement of monomeric fluorescence intensity. The variation of fluorescence intensity is also sensitive to the thermotropic phase transition of the bilayer. It is seen that in such aqueous micro- and nanoscale organized media like bile salts and lipid bilayer membranes the monomer-to-aggregate fluorescence intensity ratio reflects the state of organization of the medium.

A new fluorescent cholesterol molecular probe, 3-acetyl-7-(diethylamino)-2H-chromen-2-one attached cholesterol (Cum–Chl), has recently been introduced as a reporter of micro-heterogeneous media.

BrCH 2 COOEt (3 equiv) Zn (2 equiv) TMSCl (0.5 equiv) THF, reflux N H R EtO 2 C CO 2 Et 15 examples upto 91% yield R-CN R = aryl, heteroaryl alkyl, benzyl Abstract An efficient, zinc-mediated, single-pot and CN+3C type pseudo-four-component synthesis of 2,3,5-trisubstituted pyrrole diesters was achieved from readily available aromatic/benzylic/aliphatic nitriles and ethyl bromoacetate under trimethylsilyl chloride catalysis.

Novel water soluble robust fluorescent coumarins substituted with oligomeric alkoxy functions were synthesized by incorporating the Blaise reaction in the key step. Mono-methylated oligomeric polyethylene glycols were subjected to a three step protocol, namely (i) Michael addition to acrylonitrile, (ii) Blaise reaction with ethyl bromoacetate and (iii) condensation with 4-N,N-diethylamino-2hydroxybenzaldehyde to give fluorescent water soluble coumarins. Water solubility of the coumarins increased with the number of oxygen atoms in the side chain. However, even the most water soluble coumarin in this series can be readily extracted out of water with organic solvents like dichloromethane or ethyl acetate. Both absorption and emission spectra, recorded in four solvents, namely, hexane (nonpolar), ethyl acetate (moderately polar), methanol (polar protic) and water (highly polar and protic) displayed a bathochromic shift of the absorption (Dl max z 25 nm) and emission (Dl max z 57 nm) bands with increasing solvent polarity. The Dl max of emission is more pronounced than the Dl max of absorption, which indicates intramolecular charge-transfer (ICT) is less in the ground state compared to the excited state. Emission spectra recorded in these four solvents showed that fluorescent intensity is maximum in ethyl acetate.

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