The Relationship between Structure and Odor in the Case of Certain Derivatives of 2,2,4-Trimethyl-Δ³-cyclohexene Aldehyde¹

Enantioselective Synthesis and Olfactory Evaluation of 13‐Alkyl‐Substituted α‐Ionones

“…The key step in the conversion of 14a to 8 -10, namely a S N 2'-type reaction of an organocuprate on the allylic phosphate 20, appears to be a general method to install an alkyl substituent on the cyclohexene C¼C bond of synthetic ionones. Olfactory evaluation demonstrated that, compared to the parent (S)-a-ionone 1, the odor strength and tonality of the three analogs 8 -10 are significantly influenced by the bulkiness of the substituent at C(13), providing further evidence that hydrophobic interactions of this group play a significant role in the chemoreception of ionones [7]. In particular, the odor of the ethyl derivative 8 was found to be significantly stronger than that of the parent (S)-a-ionone (1).…”

“…In the present work, we have focused our attention on the three C(13)-alkyl-substituted a-ionone homologues 8 -10, aiming at investigating the relationship between olfactory properties and the steric bulk of the substituents on the cyclohexene C¼C bond. Already in 1941, Jitkow and Bogert reported that, in the ionone family, the violet odor depends critically on the presence of a cyclohexene nucleus, carrying at least three Me groups, two of which should be adjacent to the 3-oxobut-1-enyl chain [7]. It thus appeared reasonable to assume that an increase of the steric hindrance around C(13) would result in a variation of odor characteristics compared to that of the parent a-ionone 1.…”

Synthesis of(+)‐(2S, 6S)‐trans‐α‐Irone and of(‐)‐(2S, 6S)‐trans‐γ‐Irone

“…5: IR(film): 1700,1680, 1620, 1360, 1250,990. 'H-NMR: 6.74 (dd, J(4,3) z 16, J(4,l') z 8, H-C(4)); 6.01 (dd, J(3,4) = 16, J(3,l') z 0.5, H-C(3)); 5.28 (br. s, H-C(3')); 2.72 (ddd, J(1',4) z 8, J(1',6ax) z 6, J(l',6eq) z 2.3, H-C(1')); 2.27 (s, CH3(I)); 1.68 (ddd, J(6'ax,5'ax) z 12, J(6'ax,6eq)) N 13, J(6ax,l') N 6, Hax-C(6')); 1.5 (m. J(S'ax,6ax) N 12, J(S'ax,Ueq) z 3, J(S'ax, CH,-C(S)) z 7, Hax-C(5')); 1.43 (ddd, J(6eq,6ax) z 13, J(6'eq, 1') N 2.3, J(6'eqS'ax) z 3, Heq-C(6')); 0.79, 0.96 (2s, 2 CH3-C(4')); 0.86 (d, J z 7, CH,-C(S')).…”

“…s, H-C(3')); 2.72 (ddd, J(1',4) z 8, J(1',6ax) z 6, J(l',6eq) z 2.3, H-C(1')); 2.27 (s, CH3(I)); 1.68 (ddd, J(6'ax,5'ax) z 12, J(6'ax,6eq)) N 13, J(6ax,l') N 6, Hax-C(6')); 1.5 (m. J(S'ax,6ax) N 12, J(S'ax,Ueq) z 3, J(S'ax, CH,-C(S)) z 7, Hax-C(5')); 1.43 (ddd, J(6eq,6ax) z 13, J(6'eq, 1') N 2.3, J(6'eqS'ax) z 3, Heq-C(6')); 0.79, 0.96 (2s, 2 CH3-C(4')); 0.86 (d, J z 7, CH,-C(S')). MS: 206 (13, M+), 191 (51), 173 (7), 163 (16), 149 (22), 133 (38), 121 (53), 107 (30), 95 (41), 91 (27), 79 (13), 71 (24), 67 (13), 55 6 : 1R (film): 1700, 1680, 1620, 1360, 1250. 'H-NMR: 6.88 (dd, J(4,3) = 16, J(4,l') = 6, H-C(4)); 6.09 (dd, J(3,4) z 16, J(3,l') z 2, H-C(3)); 4.76 (m, CH2=C(2')); 3.13 (m, H-C(1')); 2.26 (s, CH,(l)); 1.87, 2.01 (AB, q, J(3',3') = 13, CHz(3')); 0.85 (d, J z 7, CH,-C(S')); 0.73,0.915 (2s, 2 CH3-C(4)), after addition of [Eu(fod),]: 4.24 (m. J(1',6'eq) z 5, J(1',6ax) z 4, J(1',4) z 6, H-C(1')); 2.27, 2.78 (AB, q, J(3',3') N 10, CH2(3')); 2.29 (ddd, J(6eq,6'ax) N 13, J(6eq,l') z 5, J(6eq,5'ax) z 3.3, H,-C(6));…”

The Importance of the 5-Alkyl Substituent for the Violet Smell of Ionones: Synthesis of Racemic 5-Demethyl-α-ionone

“…In the light of these results, we considered it interesting to analyse the odorant properties of 5-dealkyl-α-ionone 12, with the expectation that this compound would have been devoid of the typical floral and woody scent of ionones. Indeed, already in 1941, Jitkow and Bogert affirmed that the violet smell of ionones critically depends on the presence of three methyl groups attached to a cyclohexene nucleus, two of which should be adjacent to the enone side-chain [18] In this paper we describe a concise synthesis of enone 12 and its odor evaluation. At the beginning, our planned synthetic strategy ( Figure 3) was based on the preparation of the key cyclohexenylcarbinol intermediate 14, in principle obtainable through the Shapiro reaction [19] of ketone 15.…”