Treatment of ten monocyclic dienols 8-11 with an excess of fluorosulfonic acid in 2-nitropropane at -90-degrees afforded diastereoisomeric mixtures of racemic tricyclic ethers 12-14 in 81-91 % yield (see Tables 1 and 2). These transformations represent further examples of biomimetic acid-mediated cyclisations in which an OH group serves as the internal nucleophilic terminator. A non-synchronous process is postulated, and the examples described strongly re-inforce our working mechanistic hypothesis, whereby the stereochemical course of cyclisation is directed by the orientation of the side chain vicinal to the intermediate cyclohexyl cation (see Schemes 4 and 5). It is also demonstrated that the efficiency of this process is independent of the nature of the OH group, which may be primary, secondary, or tertiary. In addition, the organoleptic properties of 12 14, Me homologs of known odorants such as Ambrox(R) ((-)-3a) and its diastereoisomers, are briefly discussed.

In order to produce the important flavour compound sinensal microbial ω-hydroxylation of farnesene and its sulfone derivative were investigated. While farnesene proved to be a poor substrate, its sulfone could be hydroxylated to the ω-hydroxyfamesene sulfones in up to 27% yield. Some strains could discriminate between the E- and Z-configurated substrate. In low yields products hycroxylated at different positions and two monocyclofarnesane derivatives could also be isolated

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AbstractThe readily accessible monoterpenoid (R)‐(I) is used for the synthesis of the title compounds (R)‐(III) and (R)‐(VI), while their antipodes are prepared from (S)‐(I) by analogous routes.

AbstractTreatment of the title compounds with either H3PO4 or BF3 · Et2O affords the bridged tricyclic lactones 3 and 7 as main products (57 and 70% yield, resp.). This is an efficient and novel access to specifically functionalised molecules possesing the bicyclo[3.2.1]octane skeleton. Lactones 4 and 5 and the bicyclic ketone 6 were formed as by‐products (2, 7, and 10% yield, resp.).

Abstract(‐)‐8‐Epi‐oL‐bisabolol (I) and (‐)‐4‐epi‐β‐bisabolol (II) are identified as constituents of bergamot oil.

AbstractConformational factors have been found responsible for the dramatic change in odor between (−)‐deoxyambreinolide (12) and its (+)‐epi derivative 13. The presumably molecular event during the receptor interaction has been simulated by the diastereoisomeric 11‐methyl‐ambrox derivatives 3 and 5 as model compounds.

AbstractFrom bergamot oil (Citrus bergamia RISSO), (−)‐(4S, 8R)‐8‐epi‐α‐bisabolol (2) and (−)‐(4R, 8S)‐4‐epi‐β‐bisabolol (3) were isolated. The absolute configuration of their stereoisomers 4 and 5 was established by an enantioselective synthesis starting from (−)‐(S)‐p‐mentha‐1,8‐dien‐4‐ol.

AbstractTreatment of the title compounds (Ia) and (Ib) with either H3PO4 or BF3 ‐ Et2O affords the bridged tricyclic lactones (II) or (VI) as main products.

AbstractThe diastereoisomeric 18‐nor‐ and 19‐norambrox ((6α)‐ and (6β)‐dodecahydro‐3a,6,9a‐trimethylnaphtho[2,1‐b]furans resp.) as well as the corresponding 18,19‐dinor‐derivatives (dodecahydro‐3a,9a‐dimethylnaphtho[2,1‐b]furans) have been synthesized and subjected to sensory evaluation. Threshold data and odor determination give an enlarged insight into the structure‐activity relationship (SAR) in ambrox‐type ambergris fragrances. As a general conclusion, the accumulation of axial CH3 groups in the tricyclic ethers 1–12 leads to the strongest receptor affinity.

AbstractThe characteristic odor of the diastereomers (Va) (norlimbanol) and (Vb) is configuration dependent, the trans‐alcohol (Va) being identified as the sensorily active component.

Structural modifications of testosterone and 19‐nortestosterone have led to the synthesis of over 60 androstane and estrane derivatives whose sensory evaluation has allowed molecular parameters to be established for release of a ‘steroid‐type’ scent. Odor perception with O‐containing compounds in both classes has been found to be regioselective. Osmophoric groups at C(3) were found to be the most active and specific. Functionality at C(2) is accompanied to a large extent by anosmic defects, and O‐containing substituents at C(1) and C(4) appear to affect the receptor membrane in exceptional cases.A further characteristic of the ‘steroid‐type’ scent is diastereoselectivity. The odor intensity of axial 2‐ and 3‐hydroxysteroids is far greater than that of the equatorial epimers, and epimeric hydroxy‐groups in the 1‐, 4‐, and 5‐positions lead to almost complete absence of odor. In addition, only steroids with ‘normal’ ring junctions and configuration were found to be odorants, whereas compounds with cis‐junctions between rings A and B, or C and D, were found to be practically inactive, Steroids therefore folow the ‘triaxial rule of odor sensation’.The most remarkable feature of our findings with steroid odorants is enantioselectivityThe term ‘regioselective’ is currently used for a reaction in which formation of one structural (or positional) isomer is favored over another. For convenience we use ‘regioselective’, ‘diastereoselective’ or ‘enantioselective’ for substrate‐receptor interactions in which one positional isomer, diastereoisomer or enantiomer leads to a different sensory response (in quality and/or intensity) than another. . Whereas with C 19 ‐steroids of the ‘natural’ enantiomeric series the perception threshold is extremely low (<6 ppb), the corresponding ‘unnatural’ enantiomers have been found essentially odorless by a panel of 30 persons. This appears to be the first reported instance of a total enantioselective response to an odorant.

AbstractA series of compounds possessing a ‘Steroid‐type’ scent and related to 4‐(4′‐t‐butylcyclohexyl)‐4‐methyl‐2‐pentanones (1 and 2) has been synthesized. The odor of these compounds has been found to be dependent on their conformation; only when the molecule can assume a steroid‐like shape there is an interaction with the odor chemoreceptor.

Abstract(−)‐(S)‐2‐Hydroxy‐β‐ionone (33), (+)‐(2 S, 6 S)‐2‐hydroxy‐α‐ionone (34), and their acetates 35 and 36 have been synthesized from (+)‐(S)‐6‐methylbicyclo [4.3.0]‐non‐1‐ene‐3, 7‐dione (3). The key intermediate (+)‐(1 R, 3 S, 6 S)‐2, 2, 6‐trimethyl‐7‐oxobicyclo [4.3.0]non‐3‐yl acetate (7) was correlated with a degradation product of the pentacyclic triterpene ursolic acid (16). Compound 33 was also synthesized by an alternative route starting from (−)‐trans‐verbenol (42).

AbstractThe racemate and both enantiomers of patchouli alcohol have been synthesized by stereocontrolled routes. The olfactive properties of the patchouli alcohols prepared are reported.

Electroantennogram techniques were used to elucidate antennal olfactory response of male and female boll weevils to a dilution series of grandlure, its components, and some vicinal dimethyl analogs. At higher concentrations, response to the mixture of the two aldehyde components of grandlure was significantly higher than to the two alcohol components. Only one vicinal dimethyl analog elicited a significantly higher response than the control. There were no significant differences in response due to sex over all compounds.