A series of thiophene-fused acenes, anthra[2,3-b]thiophene (1), tetraceno[2,3-b]thiophene (2), and 2-n-decyl-tetraceno[2,3-b]thiophene (3), were synthesized. The crystal structures of 1 and 2 were determined.
A weak dipole results from the addition of the thiophene ring, and the crystal packing changes from the
triclinic structure of acenes to orthorhombic, with the molecules maintaining the herringbone arrangement
with the molecular long axis antiparallel to the neighbors. Theoretical calculation showed that the molecules
have higher oxidation potential and comparable hole mobility as acene analogues with the same number
of rings. Thin film transistor devices were fabricated from these materials. With compound 1, a field-effect mobility of 0.134 cm2/V s and on/off ratio of 108 can be achieved when deposited at a substrate
temperature of 25 °C, whereas a mobility of 0.245 cm2/V s and on/off ratio of 106 were observed for
compound 2 deposited at 80 °C.
The first series of 5′‐triazole cytidines 1a‐d and adenosines 2a‐c was prepared and evaluated for inhibitory potency toward α‐2,3‐sialyltransferase. The synthesis of target compounds was achieved by converting the 5′‐alcohol of protected nucleosides to the azide derivatives, which were then coupled with the alkynes by copper(I)‐catalyzed cycloaddition to give protected 5′‐triazole nucleosides 3a‐d/7a‐c, followed by deprotection. 5′‐Triazole adenosines 2a‐c were less efficient inhibitors of α‐2,3‐sialyltransferase than their cytidine analogues 1a‐d. 1d was the most active compound with an IC50 of 37.5 μM. These results suggested that the hydrophobic functionality and the cytidine group are clearly required for the improved binding.
A novel p-channel semiconductor pyreno[4,5-a]coronene has been synthesized and characterized. The highly fused π-conjugated framework has a twisted geometry with an excellent on-top cofacial π-π stacking in the crystal structure and with a centroid-to-centroid distance of 3.808 Å. Single-crystal field effect transistors based on the molecule exhibit a high mobility of ~0.89 cm(2) V(-1) s(-1) and an on/off ratio of ~6 × 10(4).
Racemic 7-(phenylacetamido)-1-dethia-3-aza-1-carba-2-oxacephem 3 was synthesized and found to possess antibacterial activity against Staphylococcus aureus FDA 209P, Escherichia coli ATCC 39188, Pseudomonas aeruginosa 1101-75 and Klebsiella pneumoniae NCTC 418 as well as the beta-lactamase producing organisms E. coli A9675 and P. aeruginosa 18S-H and the methicillin-resistant organism S. aureus 95. Formation of the carbacephem 3 originated from the Barton photochemical reaction in the conversion of 8 to 10. Intramolecular cyclization of syn-oximino beta-lactam 10 afforded 7-azido-2-oxa-3-azacephem 11, which was reduced and acylated to 12. Enzymatic removal of the methyl group from 12 gave the target molecule 3.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.