78814-96-7

Upstream product

• 67-56-1 methanol 
• 4561-35-7 N-nitroso-N-acetyl-DL-phenylalanine 
• 25692-18-6 methyl 2-methoxy-3-phenylpropanoate 
• 90843-50-8 α-methoxy cinnamic acid 
• 2901-75-9 (R,S)-N-acetyl phenylalanine 
• 70541-10-5 N-benzoyl-N-nitroso-DL-phenylalanine 
• 2566-22-5 DL-N-benzoylphenylalanine 

Relevant academic research and scientific papers

Cobalt-Catalyzed Asymmetric Hydrogenation of α,β-Unsaturated Carboxylic Acids by Homolytic H2 Cleavage

The asymmetric hydrogenation of α,β-unsaturated carboxylic acids using readily prepared bis(phosphine) cobalt(0) 1,5-cyclooctadiene precatalysts is described. Di-, tri-, and tetra-substituted acrylic acid derivatives with various substitution patterns as well as dehydro-α-amino acid derivatives were hydrogenated with high yields and enantioselectivities, affording chiral carboxylic acids including Naproxen, (S)-Flurbiprofen, and a d-DOPA precursor. Turnover numbers of up to 200 were routinely obtained. Compatibility with common organic functional groups was observed with the reduced cobalt(0) precatalysts, and protic solvents such as methanol and isopropanol were identified as optimal. A series of bis(phosphine) cobalt(II) bis(pivalate) complexes, which bear structural similarity to state-of-the-art ruthenium(II) catalysts, were synthesized, characterized, and proved catalytically competent. X-band EPR experiments revealed bis(phosphine)cobalt(II) bis(carboxylate)s were generated in catalytic reactions and were identified as catalyst resting states. Isolation and characterization of a cobalt(II)-substrate complex from a stoichiometric reaction suggests that alkene insertion into the cobalt hydride occurred in the presence of free carboxylic acid, producing the same alkane enantiomer as that from the catalytic reaction. Deuterium labeling studies established homolytic H2 (or D2) activation by Co(0) and cis addition of H2 (or D2) across alkene double bonds, reminiscent of rhodium(I) catalysts but distinct from ruthenium(II) and nickel(II) carboxylates that operate by heterolytic H2 cleavage pathways.

Scandium trifluoromethanesulfonate-catalyzed mild, efficient, and selective cleavage of acetates bearing a coordinative group

Scandium trifluoromethanesulfonate is a useful Lewis acid catalyst for cleavage of acetates containing coordinative groups adjacent to the acetyl carbonyl. The reaction proceeds under weak acidic conditions at room temperature. Racemizable α-keto acyloxy compounds are deacetylated without racemization. Selective mono-deacetylation at the 10-position of paclitaxel has been achieved.

Scandium trifluoromethanesulfonate-catalyzed cleavage of esters bearing a coordinative group at a vicinal position

Scandium trifluoromethanesulfonate is found to be a Lewis acid catalyst for selective cleavage of esters containing a coordinative group adjacent to an ester moiety. The reaction proceeds under weak acidic conditions at room temperature; the catalyst can be recovered and reused. Even α-acyloxy ketones are deacetylated without racemization. Selective monodeacetylation at C-10 of paclitaxel has been achieved.

THE PHOTOELIMINATION OF N-NITROSO-N-ACETYL-α-AMINO-ACIDS; A NEW SYNTHESIS OF 1,2,4-OXADIAZOLES

The excitation of N-nitroso-N-acetyl-α-aminoacids, nitrosopeptide model compounds, under neutral and weakly basic conditions, caused the homolysis of the N-N bond followed by decarboxylation to give hyponitrous acid (HNO) and N-acetylimines which were susceptible to nucleophilic addition.While weak bases caused the carboxylate group to assist intramolecular rearrangement to a small extent, they functioned primarily to provide nucleophilic NO-, which initiated nucleophilic attack leading to the C-nitroso derivatives.These C-nitroso derivatives spontaneously cyclized to 1,2,4-oxadiazoles much more rapidly than tautomerism to the corresponding oximes; the latter oximes failed to cyclize under the basic conditions.

Rearrangement of Carboxylates derived from N-Acetyl-N-nitroso-&α-amino-acids

While N-acetyl-N-nitrosophenylalanine thermally decomposes by the known mechanism, its carboxylate anion undergoes facile rearrangements initiated by carboxylate attack in methanol or water to give 2-methoxy- or 2-hydroxy-3-phenylpropanoic acid, respectively.