Synthesis and structural analysis of 2-quinuclidonium tetrafluoroborate

Abstract

Materials and Methods. Unless otherwise stated, reactions were performed in flame-dried glassware under an argon or nitrogen atmosphere using dry, deoxygenated solvents. Solvents were dried by passage through an activated alumina column under argon. Norcamphor, 3-chloroperbenzoic acid (m-CPBA), lithium aluminum hydride, sodium azide, trifluoroacetic acid (TFA), trifluoromethanesulfonimide, di-tertbutyl dicarbonate (Boc 2 O) and tetrafluoroboric acid in Et 2 O solution were purchased from Sigma-Aldrich Chemical Company and used as received. p-Toluenesulfonyl chloride was purchased from EM Science Inc. and purified prior to use. Triethylamine was purchased from Sigma-Aldrich Chemical Company and freshly distilled prior to use. Trifluoromethanesulfonic acid was purchased from SynQuest Laboratories, Inc. and used as received. 1,1-Dihydro-1,1,1-triacetoxy-1,2-benzoiodooxol-3(1H)-one (Dess-Martin periodinane, DMP) was prepared by known method 1 . Reaction temperatures were controlled by an IKAmag temperature modulator. Thin-layer chromatography (TLC) was performed using E. Merck silica gel 60 F254 precoated plates (0.25 mm) and visualized by UV fluorescence quenching, anisaldehyde or KMnO 4 staining. ICN Silica gel (particle size 0.032-0.063 mm) was used for flash chromatography. Optical rotations were measured with a Jasco P-1010 polarimeter at 589 nm. 1 H and 13 C, NMR spectra were recorded on a Varian Mercury 300 (at 300 MHz and 75 MHz, respectively). 1 H NMR spectra were reported relative to Me 4 Si (δ 0.0 ppm) or residual CHCl 3 (δ 7.26 ppm) or CHD 2 CN δ 1.94 ppm). 13 C NMR were reported relative to CDCl 3 (δ 77.0 ppm) and CD 3 CN (δ 118.69 ppm), respectively. FTIR spectra were recorded on a Perkin Elmer Paragon 1000 spectrometer and are reported in frequency of absorption (cm -1 ). High resolution mass spectra were obtained from the Caltech Mass Spectral Facility.

Unexpected reactivity and mechanism of carboxamide activation in bacterial N-linked protein glycosylation

“…5, such a distortion generates a reactive free electron pair at the nitrogen. Twisted amides are known to have a substantially higher reactivity than planar amides and were indeed proposed to have a role in biological reactions involving amide groups [33][34][35] . Backbone amide distortion has been described in crystal structures of proteins that undergo autoproteolysis 36,37 , and experimental data provide additional support that this unusual conformation of the scissile amide bond is the driving force for a nucleophilic attack during the catalysis of protein splicing 38 .…”

Schmidt Rearrangement Reactions with Alkyl Azides

“…Tani and Stoltz took advantage of this in a landmark synthesis of 2 -quinuclidonium tetrafl uoroborate 97 (Scheme 7.49 ). 96 In this work, an azide 96 bearing an azidoalkyl group placed in a position non -adjacent to the reacting ketone was treated with HBF 4 . In this way, a mixture of quinuclidinium salt 97 and the isomeric lactam 98 were formed; note that a fused lactam is not possible from this kind of substrate.…”

Acid‐Catalyzed Reactions of Twisted Amides in Water Solution: Competition between Hydration and Hydrolysis

“…The synthesis of 2-quinuclidone (TA1) has been an interesting subject for many decades, but it was not successfully prepared until 2006. [46] The twisted amides are an important class of compounds that are involved in a variety of chemical and biological processes, including the enzymatic degradation of antibiotics, [47][48][49] enzymatic isomerization of amide bonds, [50][51][52] and protein splicing, [53][54][55] and they have been extensive experimental investigations as the focus of many recent works. [56][57][58][59][60][61][62][63] Although many studies on the acid-catalyzed hydrolysis of twisted amides have been reported, the detailed mechanisms on the atomic level remain elusive.…”