Enantioselectivity in Odor Perception: Synthesis and Olfactory Properties of Iso‐β‐Bisabolol, a New Natural Product

Abstract

The odorous trace constituent iso-b-bisabolol (4) was isolated from East Indian and Western Australian sandalwood oil and synthesized by using the (E/Z)-triene 12 (iso-g-bisabolene) as a key intermediate. Only one of four stereoisomeric forms of 4, (6R,7R)-4a, is odor active, having a strong floral, muguet-like, very pleasant scent.Introduction. ± Odor perception is initiated by an interaction of a volatile stimulant with a proteinaceous receptor [1]. Different diastereoisomers and enantiomers of the same molecular structure can elicit different odor impressions, both qualitative and quantitative [2]. In our continuous search for new natural trace constituents with high odor impact, we analyzed sandalwood oils of East Indian as well as Western Australian origin [3]. The oils are obtained from wood, trunk butt, or roots of Santalum album L. and Santalum spicatum (R. Br.) A. DC. by different extraction and/or distillation techniques [4].Among a broad range of compounds, the odorless sesquiterpene alcohols abisabolol (1) and b-bisabolol (2) were detected by GC-MS analysis in both Santalum species [3a] [3b]. The corresponding iso-a-bisabolol (3) 2 ) and iso-b-bisabolol (4), however, have, to the best of our knowledge, neither been found in nature nor synthesized so far.

New Caledonian Sandalwood Oil—a Substitute for East Indian Sandalwood Oil?

“…We could identify in all three New Caledonian sandalwood oils (Z)-β-curcumen-12-ol (1.1%), (Z)-γ-curcumen-12-ol (0.6%), (Z)-12-hydroxysesquicineole (trace), 6,10-epoxybisabol-2-en-12-ol (trace), two nor-helifolen-12-al isomers (each 0.01%) and all four acorenol isomers (trace each), which were recently found for the first time in S. spicatum and/or S. album (10,15). GC-olfactometry revealed, that iso-β-bisabolol [2], a new odor active sandalwood trace constituent, having a strong floral, muguet-like, very pleasant smell (16)(17)(18) was also present in the oils from New Caledonia.…”

Phytochemistry of the heartwood from fragrant Santalum species: a review

“…[17] When dealing with essential oils, preliminary steps may involve a direct fractionation by vacuum distillation, as in the case of S. album, or more sophisticated fractionations with highly efficient spinning band [18] or Sulzer-packed columns. [19] Such distillations can be made easier after acetylation of the alcohols and regeneration of the latter by alkaline hydrolysis of selected fractions but this method is not risk-free, since artefacts can occur, such as aldehyde-enol acetates. [20] Minor odorous components, such as the cyclosantalals 152 and 153, were identified after mild oxidation to the corresponding carboxylic acids and isolation/ identification of the latter.…”

“…Chemical structures of ketones important contributor to the fragrance of the oil, with a strong floral, muguet-like odour, while its diastereoisomers 80, 82 and 83 are surprisingly odourless. [19] Whereas the odour (Z)-lanceol 75 is weak and woody, (E)-and/or (Z)-lanceal are more powerful and reminiscent of sandalwood. [80] Therefore, the contribution of lanceal(s) to the characteristic odour of the lanceol-rich essential oil of S. austrocaledonicum should be clarified.…”

“…222.37 S, [19] A, [19] AC [9] A, [10,34] S, [19] AC, [9] I [33] A, [10,34] S, [19] AC, [9] I [33] A, [10,34] S, [19] AC, [9] I [33] A, [10,34] S, [19] AC, [9] I [33] A, [10] S, [37] AC [9] *, I [33] 89 S, [37] AC [9] *, I [33] …”

“…(Z)-g-Curcumen-12-ol S, [29] AC, [9] I [33] A, [41] S, [29] AC, [9] I [33] 74 [40] (-) : A, [42] AC, [9] I [33] [27] S, [37] AC, [43] I [44] 79 [19] A, [19] AC [9] * 81 (6R,7R)-iso-b-Bisabolol h 496868-46-3 222.37 S, [19] A, [19] AC [9] …”