Gold-catalyzed 1,2-/1,2-bis-acetoxy migration of 1,4-bis-propargyl acetates: a mechanistic study.

The late transition metal catalyzed rearrangement of propargyl acetates offers an interesting platform for the development of synthetically useful transformations. We have recently shown that gold complexes can catalyze a highly selective tandem 1,2-/1,2-bis-acetoxy migration in 1,4-bis-propargyl acetates to form 2,3-bis-acetoxy-1,3-dienes. In this way, (1Z,3Z)- or (1Z,3E)- and (1E,3Z)-1,3-dienes could be obtained in a stereocontrolled manner depending on the electronic and steric features of the ancillary ligand bound to gold and the substituents at the propargylic positions. In this work, we report an experimental study on the scope of this transformation, plus a detailed theoretical examination of the reaction mechanism, which has revealed the key features responsible for the reaction stereoselectivity. Synthetic applications towards the one-pot synthesis of quinoxaline heterocycles and tandem Diels-Alder processes have also been devised.

Stereospecific debenzylative cycloetherification of carbohydrate-derived allylic alcohols, ethers and esters to form vinyl C-furanosides.

Benzyl ether protected polyhydroxylated alkene compounds containing allylic alcohol, ether or ester functionality undergo a stereospecific cyclisation reaction upon treatment with TFA-acetonitrile-toluene with inversion of configuration at the allylic position and loss of a benzyl ether to give tetrahydrofurans.

Studies on the synthesis of valienamine and 1-epi-valienamine starting from D-glucose or L-sorbose.

Two synthetic routes to a carbocyclic precursor to valienamine are reported, starting from either D-glucose or L-sorbose and using ring-closing metathesis as a key step. A low-yielding synthesis of 1-epi-valienamine is reported. Results from an abortive third possible route to valienamine based on an early introduction of nitrogen are discussed.

Practical syntheses of pyridinolines, important amino acidic biomarkers of collagen health.

The paper reports some successful results on the first fully stereoselective total synthesis of the collagen cross-link pyridinolines. All stereogenic centers are stereoselectively introduced using Williams glycine template methodology, and oxazinones are used as a source of chirality and as easily removable protecting groups of the amino acidic functionalities during the assembly of the pyridinoline nucleus.

The first total synthesis of alpha-D-glucopyranosyl-(1-->2)-beta-D-galactopyranosyl-O-pyridinoline, an important hallmark of human joint diseases.

The first total synthesis of alpha-D-glucopyranosyl-(1-->2)-beta-D-galactopyranosyl-O-pyridinoline using a short "one-pot" assembly of its 1,4,5-trisubstituted 3-hydroxypyridinium ring is reported.