Search

α,β-Unsaturated esters were selectively protected in situ in the presence of α,β-unsaturated Weinreb amides using PEt3 and trimethylsilyl trifluoromethanesulfonate (TMSOTf) in toluene under reflux. Diisobutylaluminium hydride (DIBAL-H) reduction of the mixture followed by tetra-n-butylammonium fluoride (TBAF) treatment produced α,β-unsaturated aldehydes in good yields along with the recovered α,β-unsaturated esters.

Two glycopeptides, supprescins A and B, that suppress the production of pisatin, a phytoalexin of pea, were synthesized. In the synthesis of supprescin A, condensation of 3, 4, 6-tri-O-acetyl-2-azido-2-deoxy-α-D-galactopyranosyl trichloroacetimidate or its glycosidic β isomer with N-(carbobenzoxy)-L-seryl-O-benzyl-L-seryl-glycine methyl ester was carried out in the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf) to give the monoglycosyl tripeptide derivatives. For the synthesis of supprescin B, glycosylation of 2, 3, 4, 6-tetra-O-acetyl-α-D-galactopyranosyl bromide and 1, 2, 3, 6-tetra-O-benzoyl-α-D-galactopyranose was promoted by silver trifluoromethanesulfonate (AgOTf) to provide a disaccharide derivative. The coupling of diglycosyl imidate, 2, 3, 4, 6-tetra-O-acetyl-β-D-galactopyranosyl-(1→4)-3, 6-di-O-benzoyl-2-azido-2-deoxy-D-galactopyranosyl trichloroacetimidate, and N-(carbobenzoxy)-L-seryl-O-benzyl-L-seryl-glycyl-4-benzyl-L-aspartyl-5-benzyl-L-glutamyl-O-benzyl-L-threonine methyl ester in the presence of TMSOTf afforded the diglycosyl hexapeptide derivatives. Reduction, followed by N-acetylation, and then removal of the remaining protecting groups afforded the desired supprescin B.

Formal total synthesis of (±)-aphidicolin (1) was achieved via a Lewis acid-mediated stereoselective spiroannelation reaction as a key step. The bisbenzyl acetal (2) was synthesized from the readily available dimethyl acetal (4). Treatment of 2 with trimethylsilyl trifluoromethanesulfonate (TMSOTf) afforded a 69 : 31 mixture of the spirocyclic enones (9 and 10) in excellent yield. The tricyclic ketal-ketone (3) corresponding to the B/C/D rings of 1 was easily generated from the enone (9) by intramolecular alkylation and catalytic hydrogenation as principal steps. The A-ring construction was performed by a procedure similar to one used previously. Barbier reaction of 14, followed by oxidative rearrangement, stereoselective 1, 4-addition of a methyl group, and subsequent intramolecular aldol-condensation afforded the tetracyclic enone (18), which has already been transformed into (±)-aphidicolin (1).

The aldol reaction of trimethylsilyl enol ethers (1-3) with various aldehydes in the presence of a catalytic amount of trimethylsilyl trifluoromethanesulfonate was investigated. With benzaldehyde (4) the β-hydroxycarbonyl compounds were obtained in good yields. The effect of a substituent on the benzene ring was also examined. Aliphatic aldehydes (11, 13, and 14) were found not to be suitable substrates for this catalytic aldol reaction. On treatment with tert-butyldimethylsilyl enol ethers (30 and 31) under the same conditions, benzaldehydes (4, 5, 7, 8) yielded the corresponding aldol products with good threo-selectivity.

Human peptide YY (hPYY) was synthesized in a conventional manner by assembling six peptide fragments followed by deprotection with 1 M trimethylsilyl trifluoromethanesulfonate (TMSOTf)-thioanisole in trifluoroacetic acid (TFA). After purification by gel-filtration on Sephadex G-25, followed by reversed-phase high-performance liquid chromatography, a highly purified sample of synthetic hPYY was obtained. When administered in dogs, synthetic hPYY was as active as synthetic porcine PYY in terms of the effects on systemic arterial blood pressure, and splanchnic blood flow.

A highly efficient 1, 2-trans-β-glycosidation reaction has been developed by using glycopyranosyl diethyl phosphites bearing participating groups such as benzoate, phthalimido, or trichloroethyl carbamate groups at C-2 as glycosyl donors and trimethylsilyl trifluoromethanesulfonate (TMSOTf) as a promoter.

A 37-residue peptide corresponding to the entire amino acid sequence of chicken calcitonin-gene-related peptide (cCGRP) was synthesized by successive assembling of seven peptide fragments via the azide, followed by acid treatments of protected cCGRP in two steps, i.e., first with trifluoroacetic acid (TFA) in the presence of diphenylsulfide to establish the disulfide bond between the Cys(MBzl) sulfoxide and the Cys(MBzl) residues (positions 2 and 7, respectively) and then with 1 M trimethylsilyl trifluoromethanesulfonate in TFA to remove the rest of the protecting groups employed. The synthetic peptide suppressed the 45Ca release from mouse calvaria.

Deprotection par le trifluoromethanesulfonate de trimethylsilyle. Application a la synthese de hGIP

Condensation of 3, 4, 6-tri-O-acetyl-D-glucal and trimethylsilylated nucleobases in the presence of stannic chloride or trimethylsilyl trifluoromethanesulfonate gave anomeric mixtures of 2, 3-dideoxy-D-erythro-hex-2-enopyranosyl nucleosides. The signs of the circular dichroism (CD) spectra of the anomeric 2-hexenopyranosyl nucleosides are opposite to those of usual nucleosides or glucopyranosyl nucleosides. Other examples illustrating the contribution of an unsaturated bond in the sugar portion of nucleosides to the CD spectra are also presented.

An unsulfated form of human cholecystokinin (hCCK-33) was synthesized by successive azide condensations of seven peptide fragments, followed by deprotection with 1 M trimethylsilyl trifluoromethanesulfonate/trifluoroacetic acid. The phenolic group of Tyr (position 27) was selectively sulfated with pyridine-SO3 complex, after reversible masking of other functional groups with hard base (F-)-labile protecting groups, i.e., the amino functions with 9-fluorenyl-methyloxycarbonyl group and the hydroxyl functions of 4 Ser residues with tert-butyldiphenylsilyl groups. In terms of pancreatic protein output and capillary blood flow in dogs, the relative potency of synthetic hCCK-33 with respect to that of synthetic CCK-8 (taken as 1 on a molar basis) was 0.9. In terms of gastric acid and pepsin output in rat in vivo assays, synthetic hCCK-33 was about 2- to 3-fold more potent than CCK-8 on a molar basis.

Human neuropeptide Y (hNPY) was synthesized in a conventional manner by assembling seven peptide fragments followed by reduction of the Met(O) residue with phenylthiotrimethylsilane and subsequent deprotection with 1 M trimethylsilyl trifluoromethanesulfonate (TMSOTf)-thioanisole in trifluoroacetic acid (TFA). Alternatively, deprotection was performed in a two-step manner; first, treatment with 1 M trimethylsilyl bromide-thioanisole in TFA, and then with 1 M TMSOTf-thioanisole in TFA. After purification by gel-filtration on Sephadex G-25, followed by reversed-phase high-performance liquid chromatography, a highly purified sample of synthetic hNPY was obtained in both cases. When administered in dogs, synthetic hNPY was as active as porcine NPY in terms of the effects on systemic arterial blood pressure, pancreatic blood flow, and superior mesentric artery (SMA) blood flow. Met(O)17-hNPY was found to be as active as the parent sample in these bioassays.

A 36-residue peptide amide corresponding to the entire amino acid sequence of chicken antral peptide was synthesized by assembling seven peptide fragments via the azide, followed by thioanisole-mediated deprotection with trimethylsilyl bromide and trimethylsilyl trifluoromethanesulfonate in trifluoroacetic acid.The synthetic peptide stimulated gastric secretion, but not pancreatic secretion.

Transglycosylation from acylated pyrimidine nucleoside to purines was originally developed by Miyaki, et al. To apply this method to the naturally occurring pyrimidine nucleosides having a labile sugar moiety, we studied the improvement of this reaction. As model compounds, tri-O-acetyl-3-benzoyluridine (1) and tetraacetylcytidine (2) were employed. Reaction conditions and yields were greatly improved by utilizing (1) trimethylsilyl derivatives of exo-N-acylpurines as a glycosyl acceptor, (2) trimethylsilyl trifluoromethanesulfonate as a catalyst in acetonitrile-dichloroethane. Because of the mild reaction conditions and high yield, this procedure may be regarded as a versatile method for transglycosylation, which was shown by the successful preparation of purine analogs of the polyoxin and octosyl acid nucleosides having labile amino-or anhydrosugar uronic acid.

The properties of S-benzyloxymethylcysteine, Cys(Bom), were examined. The S-Bom group is stable to trifluoroacetic acid (TFA), but is easily cleaved by treatment with silver trifluoromethanesulfonate (AgOTl)/TFA or 1 M trimethylsilyl trifluoromethanesulfonate (TMSOTf)-thioanisole/TFA. Cys(Bom) can be converted to cystine by treatment with thallium(III) trifluoroacetate.Cys(Bom)was successfully applied to the Fmoc-based solid phase synthesis of porcine brain natriuretic peptide (pBNP), a 26-residue peptide with one disulfide bond [Fmoc=9-fluorenylmethyloxycarbonyl]. In the final step, the peptide-resin was first treated with AgOTl/TFA, then with 1 M trimethyisllyl bromide-thioanisole/TFA. After dithiothreitol treatment and subsequent air-oxidation, a homogeneous pBNP was obtained in 17% yiled, based on the first amino acid loaded on the resin. The results was compared with those produced by other alternative deprotecting procedures.