Geranylated phenols

General Procedure for the Enantioselective Cyclization of Geranyl Phenol Ether Promoted by the BINOL-SnCU Complex... 

Geranyl-2,4,6-trihydrOxy-benzophenone (phenolic ketone) Tovomita krukovii (Clusiaceae) Candida albicans secreted aspartic protease (109 pM) [36]... 

Ethyl acetate, which is a comparatively small molecule, has the typical fruity character associated with all the lower esters, and a more or less equal balance between the influence of the two structural units, derived from ethyl alcohol and acetic acid. Linalyl acetate and geranyl acetate, however, although retaining the typical character of an acetate have much less of the ester fruitiness and are more closely related to the corresponding alcohols, linalool, and geraniol. The dominance of the alcohol appears to be even greater in phenylethyl acetate and paracresyl acetate (a phenolic ester). 

Dimethoxy Phenol 3,4-Dimethyl 1,2-Cyclopen tandione 5-Ethyl 3-Hydroxy 4-Methyl 2(5H)-Furanone 3-Ethyl Pyridine Furfuryl Mercaptan Geranyl Isovalerate 2,3 -Heptandione (Z)-3-Hexenyl Butyrate (Z)-3-Hexenyl Formate Hexyl Butyrate Hexyl Hexanoate Isoamyl Isobutyrate Isobutyl Formate Isobutyl Hexanoate Linalool Oxide... 

Antiseptic plant-derived phenols include phenol (Phe-OH, hydroxybenzene, carbolic acid), />-cresol (4-methylphenol), catechol (1,2-dihydroxybenzene), resorcinol (1,3-dihydroxybenzene) and pyrogallol (1,2,3-trihydroxybenzene). Other simple phenols with antimicrobial properties include some related to benzoic acid (benzenecarboxylic acid), namely salicylic acid (2-hydroxybenzoic acid), ginkgoic acid (2-hydroxy-6-(pentadec-8-enyl)benzoic acid), gentisic acid (2,5-dihydroxybenzoic acid), pyrocatechuic acid (3,4-dihydroxybenzoic acid) and gallic acid (3,4,5-trihydroxybenzoic acid). Other plant-derived phenol-related compounds include 4-methylcatechol, 1,3-dihydroxy-5-(heptadec-12-enyl)benzene, hydroquinone (1,4-dihy-droxybenzene), 1,4-dihydroxy-2-geranyl (di-isoprenyl)benzene and 4-methoxybenzaldehyde (/>-anisealdehyde). 

Geranyl-3,4,2, 4 -tetrahydrochalcone (chalcone, phenolic) Artocarpus incisus (Moraceae) [leaf] 5aR (104)... 

This methodology has been expanded to geranyl methyl carbonate for the synthesis of the vitamin E nucleus, and to tiglyl methyl carbonate for the synthesis of (—)-calanolide A and B. In the latter example, the anthracenyldiamine -based ligand was required for optimum selectivity. The synthesis of (—)-aflatoxin B lactone utilizes a dynamic kinetic asymmetric transformation, whereby a suitably functionalized phenol reacts with a racemic 5-acyloxy-2-(5//)-furanone to provide a single product in 89% yield. One final example of phenol as a nucleophile is for the deracemization of Baylis-Hillman adducts." ... 

In Chapter 6 the use of isoprene (Table 6.1) and of geranyl halides in reactions with naphthol and phenol respectively has been briefly referred to. In early work, isoprene with phenol in toluene containing 71% phosphoric acid, when reacted over 16 hours at ambient temperature (ref. 2) gave 4-(3-methylbut-2-enyl)phenol, the corresponding 2- isomer and 4-(3-methyl-3-hydroxybutyl)phenol in the phenolic products and in the neutral fraction, smaller proportions of 2,2-dimethylchroman and 6-(3-hydroxyisopentyl)-2,2-dimethylchroman. Hydrogenation of the unsaturated phenols afforded the respective 4- and 2-isopentylphenols. 

In the second approach (B), because of a low initial yield in the first method, the acid-catalysed reaction of the phenol in dioxane containing boron trifluoride etherate with the prenyl alcohol was used. In this way 2-geranyl, 2-farnesyl, 2-phytyl and 2-nonaprenylphenol were obtained in unstated yields, accompanied by the 4-isomer in each case. In the third strategy (C) the prenyl bromide was... 

A new method for the selective demethylation of alkyl methyl phosphates employs a mixture of dimethyl sulphide and methanesulphonic acid. Boron trifluoride etherate catalyses the regio- and stereo-specific alkenylation of phenolic ethers by diisopropyl prenyl or geranyl phosphates (84) in low to moderate yields. 2-(Diethoxyphosphinyl)-1,3-butadienes, e.g., (85), are cleaved by organocopper reagents in some cases this reaction is accompanied by alkylation and rearrangement to an allene structure. ... 

When geraniol reacts with phenols in the presence of acid, the common products are usually cyclized the use of 1 % oxalic acid has now been found to minimize cyclization in the reaction between orcinol and geraniol. Nerol has been labelled with deuterium in various positions [a, b, c, and d in (32)] and then converted into the chloride (33). Kinetic isotope effects on hydrolysis of (33) were measured, and 7r-participation in the cationic intermediate (34) leading to the cyclized terpinyl derivatives is discussed. Schwartz and Dunn proposed to use the complex (35), from geranyl methyl ether, as a model for a farnesol cyclization. They were not able to isolate this complex (although there was some evidence for its formation), the main complex (36%) being a dimeric a-complex (36), together with 39 % of the ketone (37), but no cyclized material. The cyclization of the acid chloride (38) to menthone and the C9 hydrocarbon (39) with tributyltin hydride, and also the optimum conditions for the cyclization of (-i-)-citronellal... 

To a stirred suspension of 176 mg sodium hydride (60% in oil, 4.4 mmol) in 20 mL THE at room temperature under argon atmosphere was added 0.376 g phenol (4.0 mmol) in portions followed by a catalytic amount of hydroquinone. The mixture was stirred for 0.5 h. HMPA (2 mL) and 0.74 mL geranyl chloride (4.0 mmol) were successively added. The whole mixture was stirred for 1 day. After decomposition of excess sodium hydride with 0.5 niL methanol, the mixture was poured onto ice water and extracted with ether. The combined organic layers were dried, concentrated, and purified by column chromatography on silica gel (hexane-dichloromethane as eluent). 

The benzylic methylene carbon signal of the prenyl or E)-3,7-dimethyl-2,6-octadienyl (geranyl) group (Cl) of phenols appears between 8 20-30. In the course of our work on prenylated phenols, we... 

Table 3. The Chemical Shifts of Methylene Carbons of Prenyl (Geranyl) Groups of Phenolic Compounds (6 in ppm)...

Fukai, T, and T. Nomura NMR Spectra of Isoprenoid Substituted Phenols. 4. Revised Structures of Albanins D and E, Geranylated Flavones from Morus alba. Heterocycles, 32, 499 (1991). 

Radula species contain many bibenzyls incorporating prenyl groups. Seven such bibenzyls (612—614,616—618,620) have been isolated from R. variabilis structures were established mainly by detailed analysis of H-NMR and mass spectra (58, 61). In (612) the presence and the location of two phenolic hydroxyls and the geranyl group were settled by comparison of the signal pattern of the aliphatic protons with those of geraniol (3) and by observation of a NOE between two aromatic protons (H-2 and H-6) and the benzylic protons (5 2.93 ppm) of the dimethyl ether. Fragment ions at mjz 91 (100%) and mjz 111 (98%) and formation of a chromane derivative (653) from (612) further supported the proposed structure (612) (Scheme 74). 

Pinene and limonene are the predominant terpenes in the leaf oil of this species. Traces of a phenol are present, and about 60 per cent, of geranyl acetate, which imparts a fine odour to the oil. Two samples... 

The oil contains about 3 per cent, of geranyl acetate, pinene, cymene, free geraniol, eucalyptol, traces of phenol (carvacrol ), and an aldehyde which is probably ouminic aldehyde. 

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