Structure and stereoanalysis of chiral flavour substances

The Nose as a Stereochemist. Enantiomers and Odor

“…Similarly, from 48b are derived (+)-(2 R c ,3 R s ,4 S c ), equatorial oxygen 47b and (−)-(2 R c ,3 S s ,4 S c ), axial oxygen, 49b . That there are differences with respect to enantioselectivity and diastereoselectivity is indicated by the odor evaluations shown below.

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Understanding allylic organocuprates: .sigma.- or .pi.-bound reagents?

“…Sir: Notwithstanding the vast array of highly valued organocuprates composed of sp2-and sp3-based ligands,2 there is a noticeable lack of successful examples involving Michael transfer of a simple allylic moiety. 3 Still fewer reports exist wherein carbon-substituted units (e.g., methailyl, prenyl, etc.) are effectively delivered.4 5*Frustration over the noncharacteristic lack of chemospecificity of allylic cuprates, especially in conjugate addition schemes,5® has lead to the proposal that x-allyl rather than cr-bound reagents (Figure 1) account for their frequent noncuprate-like behavior.51" We now report that by virtue of variable-temperature 13C NMR spectroscopy, the precise nature of allyl ligand-containing cuprates, of both the lower order (L.O.)…”

Exploiting the vicinal disubstituent effect on the diastereoselective synthesis of γ and δ lactones

“…As a final point, we show a practical application of the vic-disubstituent effect consisting of the diastereoselective synthesis of some of the most important naturally occurring cyclic esters such as the Nicotiana tabacum lactone, i.e. 2c, 24 the whisky and cognac oak lactones, 2e and 2f respectively, 25 and the Aerangis lactone, 26 i.e. 2g, and in addition the valero lactones 2h-i (Fig.…”