Synthesis and biological activity of α-aminoboronic acids, amine-carboxyboranes and their derivatives

Evaluation of oxazaborolidine activity on Streptococcus mutans biofilm formation

Dental diseases are among the most prevalent afflictions of humankind. These diseases are associated with the formation of biofilms harbouring pathogenic bacteria. Eight different derivatives of oxazaborolidines were synthesised and evaluated for their affect on Streptococcus mutans adhesion and biofilm formation. Structure-activity relationship was observed. The B-butyl moiety of the oxazaborolidines contributed an anti-adhesion effect for all derivatives, whilst its effect diminished when the boron atom was incorporated in a fused heterocyclic ring. The B-phenyl group induced bacterial adhesion in all tested compounds Oxazaborolidines may serve as novel agents for affecting oral biofilm formation. Moreover, the ability to alter the oxazaborolidine molecule and thus affect biofilms offers an excellent opportunity to study biofilm formation.

Salicylaldimine dimers derived from 2-H2NC6H4Bpin (pin = 1,2-O2C2Me4)

Condensation of salicylaldehyde (2-HOC6H4C(O)H) with 2-H2NC6H4Bpin (pin = 1,2-O2C2Me4) afforded the macrocyclic dimer 1 with an OBOBO structural unit. Similar reactivity with substituted salicylaldehyde derivatives gave the corresponding Schiff bases 2–6. Crystals of 1 were triclinic, space group P-1, a = 9.7915(4) Å, b = 10.8569(5) Å, c = 12.8445(6) Å, α = 102.067(1)°, β = 96.011(1)°, γ = 90.458(1)°, Z = 2. All new compounds have been tested for their antifungal activity against Aspergillus niger and Aspergillus flavus.Key words: antifungal, boron, dehydration, heterocycles, Schiff bases.

Synthesis and catalysed hydroboration of styryl sulfonamides

We have prepared the aryl sulfonamides 4,4′-R-C6H4SO2NHC6H4CH=CH2 (R = CH3, 1a; NO2, 1b) by addition of 2 equiv. of 4-vinylaniline to the corresponding sulfonyl chlorides. The disulfonamides 4,4,4′-(R-C6H4SO2)2NC6H4CH=CH2 (R = CH3, 2a; NO2, 2b) were also prepared using 4-vinylaniline and 2 equiv. of the sulfonyl chlorides in the presence of DMAP. Although hydroborations of sulfanilamide derivatives 1 suffered from competing hydrogenation reactions, judicious choice of the transition metal catalyst gave selective formation of either the primary or secondary boronate esters in hydroborations of 2a.Key words: boronate esters, catalysed hydroborations, sulfanilamides, vinylaniline.

Platinum pyridinecarboxaldimine complexes containing boronate esters

Condensation of 2-pyridinecarboxaldehydes with 2-, 3-, and 4-H2NC6H4Bpin (pin = 1,2-O2C2Me4) gave the corresponding boron-containing pyridinecarboxaldimines (N–NBpin). Addition of these ligands to [PtCl2(coe)]2 (coe = cis-cyclooctene) gave complexes of the type cis-PtCl2(N–NBpin) in moderate yields. The platinum complexes have been examined for their potential cytotoxicities against OV2008 (human ovarian carcinoma) and the analogous cisplatin-resistant cell line C13. Key words: boronate esters, pyridinecarboxaldimines, cytotoxicity, platinum, boron.

Identification of a potent and rapidly reversible inhibitor of the 20S-proteasome

Synthesis and in vitro characterization of novel, lactam boronic acid based, selective, and rapidly reversible inhibitor 14 of the 20S-proteasome is presented.