Sesquiterpene tetracyclic

Although cedranoid sesquiterpenes have earlier been synthesized, a renewed interest in alternative methods for elaborating these frameworks has arisen. The stereo-specific approach to (x-cedrene and a-patchoulene skeletons designed by Deslong-champs and summarized in Scheme XLIII is a case in point Beginning with the Stork-Clarke intermediate 559, the tetracyclic cyclopropyl diketone 560 was elaborated via a series of standard transformations. Treatment of 560 with three equivalents of sodium methoxide in methanol at room temperature for 20 min... 

NT528 Fujimori, T., R. Kasuga, H. Kaneko, Set al. Isolation and structure determination of solanascone, a new tetracyclic sesquiterpene ketone from Nicotiana tabacum. Tennen Yuki Kagobutsu Toronkai Koen Yoshishu 1978 417. 

An intramolecular nitrile oxide cycloaddition also served as the key step in the stereoselective assemblage of the skeleton of angular triquinane sesquiterpenes of the isocomene series. Tetracyclic isoxazoline 203 was obtained from oxime 202 [derived from tetrahydroindandione 201] and on treatment with sodium hypochlorite... 

Artemisinin 1, a naturally occurring sesquiterpene peroxy-lactone, has been isolated in up to 0.25% yield from the dry leaves of Artemisia annua L.1 Interest in artemisinin is based on its phytomedicinal properties. In 168 b.c. China, as described in a Treatment of 52 Sicknesses, the leaves of A. annua (Qinghao) were used for the treatment of chills and fever.2 It was not until 1972 that the active antimalarial agent qinghaosu was isolated in pure form. This allowed for the unequivocal elucidation of its structure through the use of x-ray crystallography. This complex tetracyclic peroxide is now referred to as artemisinin in various sources such as Chemical Abstracts or the Merck Index. 

The cyclopropanated furanone 32 was found to behave as a Diels-Alder diene. Thus, 32 reacts with maleic anhydride (33) to give a tetracyclic adduct 34 which is formed endoselectively (Scheme 9) (93SL415). The latter adduct is a spiroannulated butenolide related to naturally occurring sesquiterpenes [85AG(E)94 85TL5453],... 

The photo-cycloaddition of ethylene to 3-alkoxy chromones such as 315 has been applied to the synthesis of marine sesquiterpene filiformin and congeners (Scheme 43) <1996JOC4391>. Tandem [2+2] 7i-photo-cycloaddi-tion and y-hydrogen abstraction provided tetracyclic intermediate 316 which was converted to terpene 317 by subsequent oxetane ring reduction and acid-catalyzed rearrangement. 

Fleck, M. and Bach, T. (2008) Total synthesis of the tetracyclic sesquiterpene ( )-Punctaporonin C. Angewandte Chcmie, International Edition, 42, 6189-6191. 

As depicted in Scheme 44 some further transformations of the tetracycles such as 148 have allowed the synthesis of tryciclic cyclooctenes (149), present in many sesquiterpenes. For these recent studies they have used catalytic conditions for the PKR of diendiyne 147 mediated by Rh, Ir or Co complexes [154]. 

A stereoselective Li-NHs reduction of a cyclopentenone has been employed in two different syntheses of the cytotoxic sesquiterpene coriolin (69 Scheme 2). In one synthesis, tricyclic ketone (70) was reduced stereoselectively to alcohol (71) using Li-NHs-methanol. In the second synthesis, tetracyclic enone (72) was converted in a single step to (71). This reduction proceeds by initial cleavage of the cyclopropyl ketone unit of (72) to give ketone (70), which is then reduced to (71). 

Pogostemon cablin (Blanco) Benth. -oriza, patchouli, patcholi, patchuli Tranquilizer, for a calming effect Leaf (decoction or infusion, ingested) Caboclos [51,56] Essential oils [153,154,155,156] patchoulic alcohol [157,158] sesquiterpene hydroperoxides [159] flavonoids [160,161] tetracyclic sesquiterpene [162,163,164], ... 

This rearrangement is illustrated by a new synthetic approach to cyclosativene and similar tetracyclic sesquiterpenes based on the rearrangement of such a methylenenorbornene 26 which occurred to give 27 in 87% yield on simple treatment with A -bromosuccinimide in aqueous dimethyl sulfoxide. ... 

Steroids are formed from two sesquiterpene molecules—farnesyl pyrophosphate— which are attached to each other tail to tail to give the acyclic squalene (SOC-atoms) this undergoes complex reactions involving a cyclisation to tetracyclic or pentacychc ring systems, especially cholesterol. 

A six-step synthetic approach to the tetracyclic skeleton of neurotrophic sesquiterpene merrilactone A, using intramolecular photocycloaddition to form the oxetane ring, was reported.902 Irradiation of a degassed acetonitrile solution of 262 gave the product 263 (Scheme 6.108) in a very high yield (93%). This reaction creates three stereocentres in two new rings, forming an oxa[3.3.3]propellane framework. 

The isolation and structural elucidation of the novel tetracyclic sesquiterpenes ishwarane (311, R = and ishwarone (311, R = O), obtained from the... 

Rao et al. isolated ishwarone (391) as one of the chief constituents of the roots of A. indica [347], Subsequent investigations by Ganguly et al. and Govindachari et al. led to the first structural assignment of ishwarone (391) as a novel tetracyclic sesquiterpene ketone based on eremophilane skeleton, the first of its kind to occur in the nature [348,349]. Ishwarane (388), reported from the roots of A. indica by Govindachari et al. is the first tetracyclic sesquiterpene hydrocarbon based on the eremophilane skeleton [334], A tetracyclic sesquiterpene alcohol, ishwarol (389) is also reported from the roots of A. indica [350]. Pakrashi et al. isolated (125)-... 

Of the carbocyclic sesquiterpenes found in Eremophila, the most elaborate are the tetracyclic enr-zizaenes (89,90,92,93). One possible sequence for the assembly of such a nucleus is given in Scheme 24. Cyclization of 2E,6Z-farnesyl pyrophosphate between the 1 and 6 position would generate the bisabolonium cation equivalent which, after a hydride shift, could further cyclize to a spiro carbocation. The tricyclic ring system can then be assembled by invoking alkylation of the cyclohexene double bond. The tertiary carbocation generated incorporates a bicyclo[3.2.1]octane system which can rearrange in two ways leading to the tricyclic sesquiterpenes metabolites found in Eremophila. 

C.5H24, Mr 204.36, oil, bp. 80-82 C (133 Pa), [a]o -40° CHCI3). Example of the small group of tetracyclic sesquiterpenes, first isolated from the roots of the Indian birthwort (Aristolochia indica, Aristolochia-ceae). The plant also contains ishwarol (C,sH240, Mr 220.35). 

Marasmane sesquiterpenes, possibly resulting from contraction of the cyclobutane ring of the protoilludane skeleton (Scheme 1), can be divided into two groups tricyclic (Part 6) and heterocyclic (tetracyclic) (Part 7). The tricyclic constituents were divided into three subgroups simple marasmanes (6.1-6.8), isomarasmanes (6.9-6.11) and 13-normarasmanes (6.12-6.22). 

Daniewski, W.M., M. Kocor, and S. Thoren Constituents of Higher Fungi. Part VIII. Isolactarorufin, a Novel Tetracyclic Sesquiterpene Lactone from Lactarius rufus. Heterocycles, 5, 77 (1976). 

Ishwarane (20) and ishwarone (25) are two novel tetracyclic sesquiterpenes which have been isolated from Aristolochia indica Linn, and other tropical plants a synthesis of ishwarane was reported by Kelly and his co-workers in 1971. Kelly and Alward have now effected an improved synthesis of the hydrocarbon, which... 

Ishwaranes represent 7-11/10-12-bicycloeremophilanes. These rare tetracyclic sesquiterpenes are found in Aristolochiaceae, for example ishwarane itself and ish-waranol in the roots of Aristolochia indica and 3-ishwaranone from Aristolochia debilis. 

Nayak, U. R., and Sukh Dev Studies in Sesquiterpenes. XXXV. Longicyclene, the First Tetracyclic Sesquiterpene. Tetrahedron 24,4099 (1968). 

In the sesquiterpene series, a-, mono-, bi-, tri-, and tetracyclic compounds are known (Fraga, 1991). Of these, bi-cyclic and tricyclic compounds predominate. Most sesquiterpenes occur free, although glycosides of this series are known (Wong et al., 1991). 

Presently, sesquiterpenoids (128, 237, 305, 333, 376) constitute the largest single class of terpenoids, with over 2500 well-defined (only C15) compounds, embracing some 120 distinct skeletal types from acyclic to tetracyclic. Sesquiterpenoids encompass a most impressive array of carbocyclic ring systems, and this diversity and novelty have stimulated outstanding synthetic activity in this field (184). Figure 8.1.8 depicts the important sesquiterpene skeletal types most widely distributed in nature and often encountered as constituents of wood extractives. 

From the roots of Aristolochia indica, the tetracyclic sesquiterpenes ishwarane (252) and ishwarone (253) have been isolated (314). A few other related compounds are known. Biogenetically, they appear to be derived from the nootkatane cation (240). 

---