Investigating the Effects of Donors and Alkyne Spacer on the Properties of Donor-Acceptor-Donor Xanthene-Based Dyes.

NIR dyes have become popular for many applications, including biosensing and imaging. For this reason, the molecular switch mechanism of the xanthene dyes makes them useful for in vivo detection and imaging of bioanalytes. Our group has been designing NIR xanthene-based dyes by the donor-acceptor-donor approach; however, the equilibrium between their opened and closed forms varies depending on the donors and spacer.

Thienylpiperidine Donor NIR Xanthene-Based Dye for Photoacoustic Imaging.

Few xanthene-based near-infrared (NIR) photoacoustic (PA) dyes with absorbance >800 nm exist. As accessibility to these dyes requires long and tedious synthetic steps, we designed a NIR dye () with thienylpiperidine donors and a xanthene acceptor that is accessible in 3-4 synthetic steps. The dye boasts a strong PA signal at 880 nm with good biological compatibility and photostability, yields multiplexed imaging with an aza-BODIPY reference dye, and is detected at a depth of 4 cm.

New Design Strategy Toward NIR I Xanthene-Based Dyes.

An effective design strategy with an efficient synthetic route to xanthene-based far-red to near-infrared dyes is reported. The dyes were prepared by the Suzuki cross-coupling of the electron-poor fluorescein ditriflate with the electron-rich boronic acid/ester-functionalized pyrrole () and indole () moieties. Upon treatment with trifluoroacetic acid, the closed nonfluorescent forms of the dyes ( and ) ring-opened to their fluorescent forms ( and ).

Donor-Acceptor-Donor NIR II Emissive Rhodindolizine Dye Synthesized by C-H Bond Functionalization.

A NIR II emissive dye was synthesized by the C-H bond functionalization of 1-methyl-2-phenylindolizine with 3,6-dibromoxanthene. The rhodindolizine () spirolactone product was nonfluorescent; however, upon opening of the lactone ring by the formation of the ethyl ester derivative, the fluorophore absorbs at 920 nm and emits at 1092 nm, which are both in the NIR II region. In addition, 4-cyanophenyl- () and 4-methoxyphenyl-substituted rhodindolizine () could also be prepared by the C-H activation reaction.

Synthesis of 2,5-Dibutyl-3,6-dimethyl-1 H,2 H,4 H,5 H-pyrrolo[3,4- c]pyrrole-1,4-dione: A Diketopyrrolopyrrole Scaffold for the Formation of Alkenyldiketopyrrolopyrrole Compounds.

This manuscript describes an unprecedented and efficient synthesis of a new DPP scaffold, 2,5-dibutyl-3,6-dimethyl-1 H,2 H,4 H,5 H-pyrrolo[3,4- c]pyrrole-1,4-dione (DMDPP), containing methyl groups at the 3,6-positions as a precursor to preparing 3,6-divinyl-substituted DPP compounds. Subsequently, following the synthesis of DMDPP, we performed an efficient and mild C-H functionalization of the methyl groups with a variety of aromatic aldehydes to synthesize the first examples of 3,6-divinyl-substituted DPP compounds in moderate to good yields.

Cycloalkyl-aminomethylrhodamines: pH dependent photophysical properties tuned by cycloalkane ring size.

A series of fluorescent pH probes based on the spiro-cyclic rhodamine core, aminomethylrhodamines (AMR), was synthesized and the effect of cycloalkane ring size on the acid/base properties of the AMR system was explored. The study involved a series of rhodamine 6G (cAMR6G) and rhodamine B (cAMR) pH probes with cycloalkane ring sizes from C-3 to C-6 on the spiro-cyclic amino group. It is known that the pKa value of cycloalkylamines can be tuned by different ring sizes in accordance with the Baeyer ring strain theory.

Anilinomethylrhodamines: pH sensitive probes with tunable photophysical properties by substituent effect.

A series of pH dependent rhodamine analogues possessing an anilino-methyl moiety was developed and shown to exhibit a unique photophysical response to pH. These anilinomethylrhodamines (AnMR) maintain a colorless, nonfluorescent spirocyclic structure at high pH. The spirocyclic structures open in mildly acidic conditions and are weakly fluorescent; however, at very low pH, the fluorescence is greatly enhanced.

pH-dependent Si-fluorescein hypochlorous acid fluorescent probe: spirocycle ring-opening and excess hypochlorous acid-induced chlorination.

We report the synthesis and characterization of a fluorescent probe (Hypo-SiF) designed for the detection of hypochlorous acid (HOCl) using a silicon analogue of fluorescein (SiF). The probe is regulated in an "off-on" fashion by a highly selective thioether spirocyclic nonfluorescent structure that opens to form a mixture of fluorescent products in the presence of HOCl. Over a range of pH values, the probe reacts with a stoichiometric amount of HOCl, resulting in a mixture of two pH-dependent fluorescent species, a SiF disulfide product and a SiF sulfonate product.

A mild synthesis of unsymmetrical bisalkoxysilanes through catalyzed alcoholysis of hydridosilanes containing C-C multiple bonds and aryl halides.

The synthesis of unsymmetrical bisalkoxysilanes containing unsaturated C-C bonds and alkyl and aryl bromides has been developed. This method is a modification of our previously reported two-step procedure that utilizes readily available catalysts (rhodium acetate dimer and manganese pentacarbonyl bromide) under mild neutral aprotic conditions. Good to moderate yields of the products were obtained in a short period.

Binding and inhibition of Cdc25 phosphatases by vitamin K analogues.

A synthetic K vitamin analogue, 2-(2-mercaptothenol)-3-methyl-1,4-naphthoquinone or Cpd 5, was previously found to be a potent inhibitor of cell growth [Nishikawa et al., (1995) J. Biol.