Sesquiterpene tricyclic

Schimmel Co. showed that by treating caryophyllene hydrochloride melting at 69° (68° to 70°) with sodium ethylate, an unsaturated tricyclic sesquiterpene resulted. This body has the following characters —... 

Two distinct sesquiterpenes exist in the essential oil of Santalum album, known as a-santalene and /3-santalene. 8-santalene is probably a bicyclic and a-santalene a tricyclic sesquiterpene. These sesquiterpenes were discovered by Guerbet. From the method of their preparation it is doubtful whether they have been obtained in a state of purity, so that the characters assigned to them must be accepted with some reserve, and as probably being only approximate. 

Semmler considers /3-gurjunene to resemble the tricyclic sesquiterpene, cedrene, so that it is doubtful whether it is bicyclic or tricyclic. 

This body is apparently a tricyclic sesquiterpene. It was isolated from essential oil of Herabol myrrh by Von Friedrichs/- who found it to have the following characters —... 

It yields a characteristic reaction with bromine. If a few drops are, dissolved in 3 c.c. of glacial acetic acid and a little bromine vapour allowed to pass down the tube, a fine crimson colour forms which rapidly extends to the whole of the liquid and soon changes to violet and then to indigo blue with phosphoric acid, the acetic acid solution gives a rose madder colour at the junction of the liquids, and when the liquids are mixed, the colour changes to crimson and then slowly to violet. Baker and Smith consider that the sesquiterpene contains one double linkage. Semmler considers that it is a mixture of at least two bodies, one a bicyclic and the other a tricyclic sesquiterpene. 

The essential oil from the oleo-resin of Chinese turpentine (botanical origin unknown) contains a tricyclic sesquiterpene, having the following characters —... 

By the action of phosphorus pentachloride it yields betulyl chloride, a partial molecular rearrangement having apparently taken place, since, on hydrolysis, it yields a tricyclic betulol which is of particular interest in that it is the first tricyclic sesquiterpene alcohol of a crystalline character to be discovered. Its characters are as follows —... 

Longifolene is a tricyclic sesquiterpene. It is a typical terpene hydrocarbon in terms of the structural complexity. The synthetic challenge lies in construction of the bicyclic ring system. Schemes 13.24 through 13.33 describe nine separate syntheses of longifolene. We wish to particularly emphasize the methods for carbon-carbon bond formation used in these syntheses. There are four stereogenic centers in longifolene,... 

Its structure constitutes being a heterocyclic analog of naturally occurring tricyclic sesquiterpenes (Scheme 2.126). 

The utility of the electrohydrocyclization reaction to assemble natural products remains essentially untapped. It has, however, been used in the synthesis of the tricyclic sesquiterpene 1-sterpurene (3), the presumed causative agent of the so-called silver leaf disease that effects certain species of scrubs and trees in Western North America [15]. As is illustrated in Scheme 1 and in Table 2, the electrohydrocyclization reaction of bisenoate (5) was used to create the five-membered ring of the natural product. 

The tricyclic sesquiterpene longifolene has served as a vehicle for the illustration of new strategies for organic synthesis.25 Both enantiomers have been obtained from natural sources (-i-)-longifolene occurs in several Firms species and is commercially available while the rare (—)-longifolene has been found in certain liver mosses.2 We elected to prepare (—)-longifolene 49 from the cyclohexa-1,4-diene 45, obtained from the Birch reduction-alkylation of benzoxazepinone 9 in 96% yield with a diastereomeric excess of greater than 98% (Scheme 13).22... 

In a novel total synthesis of the tricyclic sesquiterpene (—)-longifolene, an intramolecular diazoalkane cycloaddition to a cyclohexadienone ring followed by thermal ring contraction of the resulting pyrazoline gave the tricychc vinylcyclo-propane 261 and this constitutes the key steps in this synthesis (314) (Scheme 8.63). The interesting features of this sequence are the separation of dipole and dipolarophile by five atoms and the formation of a seven-membered ring in the cycloaddition step. 

Intramolecular [2 + 2] photocycloadditions of 3-alkenylcyclopent-2-enones represent the key step in the total synthesis of various natural products, e.g. pentalenolactone 6-methyl ester19 and pentalenic acid,20 as well as in the preparation of strained fenestranes21 and laurenene.22 Similarly, the photoisomerization of 3-alkenylcyclohexcnoncs to tricyclo[6.3.0.01-6]undecanones are steps in the syntheses of tricyclic sesquiterpene isocomene23 and precursors to members of the acorane family.24... 

Synthetic applications of these photocycloadditions to aromatic compounds are sometimes hampered by low chemical yields and poor selectivity in the photoreactions. However, a number of elegant syntheses of tricyclic sesquiterpenes have been hased on intramolecular 1,3-phutocycloadditions ie.g. 3. SI), and these represent a completely new approach to the preparation of such systems. 

From the marine sponge Haliclona sp. (also known as Adocia sp.), a family of hexaprenoid hydroquinones called adociasulfates, have been recently reported as inhibitors of kinesin motors [100,101], These types of compounds were also found in several soft corals, such as Lemnalia africana [102], Okinawan soft coral of Nephthea sp. [103], and the gorgonian Alertogorgia sp., which yielded the cytotoxic tricyclic sesquiterpene, suberosenone [104],... 

Table 2. Tricyclic Sesquiterpene Isothiocyanates Isolated from Sponges...

The three mono-epoxides of humulene 1 are naturally occurring, and it is believed that they are in vivo precursors of other bicyclic and tricyclic sesquiterpenes. In vitro experiments have demonstrated that the 1,2- and 4,5-epoxides undergo facile acid-catalysed rearrangement, and it has been shown recently that treatment of a chloroform solution of the 8,9-epoxide with tin(IV) chloride at -60°C for 15 minutes gives a variety of hydrocarbons and one major product (25%), the alcohol 2. 

Xu X-H, Zeng L-M, Su J-Y (1997) Tricyclic Sesquiterpene from Laurencia majuscula. Chem Res Chin Univer 13 176... 

Bach, T. (2002) Stereoselective total synthesis of the tricyclic sesquiterpene (i)-kelsoene by an intramolecular Cu(I)-catalyzed [2 + 2]-photocycloaddition reaction. Synlett, 1305-1307. 

Mehta, G. and Sreenivas, K. (2002) Enantioselective total synthesis of the novel tricyclic sesquiterpene (—)-sulcatine G. Absolute configuration of the natural product. Tetrahedron Letters, 43, 3319-3321. 

The same synthetic route was applied to the preparation of the tricyclic sesquiterpene santalol 235). The reaction of the tricyclic aldehyde 435 with ethylidene-triphenylphosphorane and paraformaldehyde 205 gives the a,P-unsaturated alcohol 436, elimination of phosphorus being probably directed by the thermodynamical stability of 436 235) (Scheme 76). 

The related tricyclic sesquiterpene patchoulol (48a) is a good substrate for microorganisms and hy-droxylation at various sites can be accomplished, for example at C-S by Choanephora circinana in 74% yield (equation 14). Hydroxylation of the methyl group on C-4 can be accomplished by PenicUlium ru-brum FX-318 in 75% yield,and of the C-14 methyl group in (lf )-caryolan-l-ol (48b) by Aspergillus niger (MMP 521) in 26% yield. ... 

Wagner-Meerwetn rearrangement. Exposure of 2 to 0.3 equiv. of TsOH in refluxing benzene effects rearrangement to the tricyclic sesquiterpene iso-comene (3). ... 

Cycloaddition of the endocyclic 2-siIyloxydiene (106) to methyl vinyl ketone gave die tncy-clo[2.2.2]octenes (107) with a silyloxy-directed regiochemistry. The major endo product was then transformed into the tricyclic sesquiterpene ( )-seychellene (108) (Scheme 29). ... 

The reagent has been used in a highly. stereoselective total synthesis of the racemic form of the tricyclic sesquiterpene seychellene (8), a minor component of commercial... 

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