Synthesis and odor of optically active 2-n-hexyl- and 2-n-heptylcyclopentanone and the corresponding δ-lactones

(−)‐R‐Mevalonolactone Studied by ROA and SERS Spectroscopy

“…For example, δ‐lactone are widely found in different kinds of fruits and plays important roles in their flavours flavors . It was also found that the enantiomeric pairs of δ‐lactones differ in odor and threshold of perception . The whole class of δ‐lactones are statins, which are currently the top‐selling cholesterol‐lowering drugs in the world .…”

“…9,10 It was also found that the enantiomeric pairs of δ-lactones differ in odor and threshold of perception. 11 The whole class of δ-lactones are statins, which are currently the top-selling cholesterol-lowering drugs in the world. 12 Some of them, like simvastatin and lovastatin, are administered directly as δlactone prodrugs, which upon conversion to their respective hydroxy acid serve as strong competitive inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase).…”

SpinPhox/Iridium(I)‐Catalyzed Asymmetric Hydrogenation of Cyclic α‐Alkylidene Carbonyl Compounds

“…[6] The iridium complexes of chiral P,N ligands are particularly noteworthy in overcoming these limitations, [7] and demonstrated excellent enantioselectivities in the AH of a wide range of largely unfunctionalized olefins, [8] including olefins with weakly coordinating groups [9] and tetrasubstituted olefins. [11] Nevertheless, challenges still remain in the AH of exocyclic a,b-unsaturated cyclic carbonyls with regard to the limited substrate scope, and the enantioselectivities are often strongly dependent on the ring size of the substrates in the AH of a-alkylidene lactams and lactones, [3][4][5] as indicated by BiphPhox/Ir I catalysts ( Figure 2). [11] Nevertheless, challenges still remain in the AH of exocyclic a,b-unsaturated cyclic carbonyls with regard to the limited substrate scope, and the enantioselectivities are often strongly dependent on the ring size of the substrates in the AH of a-alkylidene lactams and lactones, [3][4][5] as indicated by BiphPhox/Ir I catalysts ( Figure 2).…”

“…[1] An attractive synthetic route to these compounds would be the catalytic asymmetric hydrogenation (AH) of the C = C bonds in the exocyclic a,b-unsaturated cyclic carbonyls, by virtue of the high efficiency, atom-economy, and cost-effectiveness of the methodology. While a great number of chiral catalysts have been developed over the years for AH of various acyclic and endocyclic unsaturated carbonyl compounds, [2] documented examples which are especially effective for the AH of the exocyclic C = C bonds of a-alkylidene lactams, [3] lactones, [4] and/or cyclic ketones [5] are still quite rare. The difficulty associated with this type of substrate in asymmetric hydrogenation is probably due to the exocyclic nature of the C=C bond which may hamper substrate bonding to the metal center, and has been assumed to be a key factor in achieving high activity and good stereocontrol in the rhodium-or ruthenium-catalyzed AH.…”

“…[10] In this context, a few excellent iridium catalysts have been developed recently for AH of C=C bonds in a,b-unsaturated carbonyl compounds as well, as exemplified by the independent pioneering studies of the groups of Bolm, Hou, and Zhou. [11] Nevertheless, challenges still remain in the AH of exocyclic a,b-unsaturated cyclic carbonyls with regard to the limited substrate scope, and the enantioselectivities are often strongly dependent on the ring size of the substrates in the AH of a-alkylidene lactams and lactones, [3][4][5] as indicated by BiphPhox/Ir I catalysts ( Figure 2). [12] We previously reported a class of chiral iridium(I) complexes, SpinPhox/Ir I (Figure 2), with spiro P,N ligands [13] for efficient AH of ketimines, a,b-unsaturated carboxylic acids, and Weinreb amides, as well as a,a'-bis(2- [*] X.…”