SNAP-Tag-Targeted MRI-Fluorescent Multimodal Probes

Magnetic resonance imaging (MRI) is a powerful imaging modality, widely employed in research and clinical settings. However, MRI images suffer from low signals and a lack of target specificity. We aimed to develop a multimodal imaging probe to detect targeted cells by MRI and fluorescence microscopy. We synthesized a trifunctional imaging probe consisting of a SNAP-tag substrate for irreversible and specific labelling of cells, cyanine dyes for bright fluorescence, and a chelated GdIII molecule for enhancing MRI contrast. Our probes exhibit specific and efficient labelling of genetically defined cells (expressing SNAP-tag at their membrane), bright fluorescence and MRI signal. Our synthetic approach provides a versatile platform for the production of multimodal imaging probes, particularly for light microscopy and MRI.

Enantioselective assembly of tertiary stereocenters via multicomponent chemoselective cross-coupling of geminal chloro(iodo)alkanes

Tertiary stereocenters represent a ubiquitous and highly important motif in many pharmaceutically active compounds and natural products. Development of efficient and straightforward approaches to their enantioselective construction from readily available simple substrates is an important yet challenging goal for synthetic chemistry. Herein we describe an efficient, versatile and facile method for the highly enantioselective construction of tertiary stereocenters via unprecedented consecutive one-pot Suzuki reactions of non-activated racemic 1-chloro-1-iodoalkanes with alkylboranes. It represents the first cross-coupling approach which employs simple and readily available primary alkyl substrates for the direct multicomponent assembly of enantioenriched tertiary stereocenters. A simple and effective preparation of 1-chloro-1-iodoalkanes from ubiquitous α-chloroalkanoic acids is also described. Collectively, the developed methods open a door to efficient catalytic enantioselective synthesis of alkanes bearing tertiary stereocenters from carboxylic acids just in few steps.

Efficient synthesis of secondary alkyl fluorides via Suzuki cross-coupling reaction of 1-halo-1-fluoroalkanes

Organofluorine compounds have found extensive applications in various areas of science. Consequently, the development of new efficient and selective methods for their synthesis is an important goal in organic chemistry. Here, we present the first Suzuki cross-coupling reaction which utilizes dihalo compounds for the preparation of secondary alkyl fluorides. Namely, an unprecedented use of simple 1-halo-1-fluoroalkanes as electrophiles in C(sp(3))-C(sp(3)) and C(sp(3))-C(sp(2)) cross-couplings allows for the formal site-selective incorporation of F-group in the alkyl chain with no adjacent activating functional groups. Highly effective approach to the electrophilic substrates, 1-halo-1-fluoroalkanes, via iododecarboxylation of the corresponding α-fluorocarboxylic acids is also presented. The conceptually new route to organofluorides was used for the facile preparation of biomedically valuable compounds. In addition, we demonstrated that an asymmetric version of the developed reaction for the stereoconvergent synthesis of chiral secondary alkyl fluorides is feasible.