Cycloartane derivatives

A new method for the degradation of the typical iso-octenyl side-chain of tetracyclic triterpenoids has been reported. The key step involves N-lithioethylene-diamine-induced double-bond isomerizations of the olefin (50), obtained by lead tetra-acetate decarboxylation of the trisnoracid (51), to a mixture of (52) and (53). The details of the n.m.r. spectra of 45 cycloartane derivatives have been described and assignments made for the methyl group signals. "... 

In plants cycloartanes occur in the free state and in the form of glycosides. The methods of isolation fi-om plant raw material, developed for various types of triterpenoids, are fully applicable to the cycloartane derivatives. 

The side chain m. Astragalus cycloartane sapogenins and saponins may be of different type (Table 1) side chain with acyclic construction, or with tetrahydrofuranic ring at C-17 (20,24-epoxy cycloartane, the most rapresentative side chain as in cycloastragenol, 18), or with a tetrahydropyranic ring (20,25-epoxy and 16,23-epoxy cycloartane derivatives) and with two condenced epoxy ring (16P,23 16a,24-diepoxycycloartane compounds). All these chains influence the signals of the carbons and protons involved and that of the vicinal atoms [147,219]. 

Gan LX, Han XB, Chen YQ (1986a) Astrasieversianins IX, XI and XV, cycloartane derived saponins from Astragalus sieversianus. Phytochemistiy 25(6) 1437-1441... 

Cycloartanes are found in the plants in free states as well as in the glycosidic form. Over than 100 saponins, mainly derivatives of the 20(R),24(S) form of 90, 19 cyclolanost-24-ene-30-ol (cycloastragenol), named astragalosides or astraversianins, and more rarely the 20(S), 24(R) form (cyclogalegenin), named cyclogaleginosides and sieberosides have been so far isolated (Table 3). Some species also contain trihydroxyolean-12-ene saponins (Table 4). 

Astragaloside II, a cycloartane triterpene glycoside isolated from the Egyptian Astragalus spinosus, was tested at minimum of five concentrations 10-fold dilution against a total of 60 human tumor cell lines derived from seven cancer types (lung, colon, melanoma, renal, ovarian, brain and leukemia). The results indicated that the colon cancer (SW-620) and the leukemias (CCRF-CEM, HL-60) were the most sensitive cell lines [98]... 

The full paper on the synthesis of pollinastanol from cycloartanol has been published.21 The revision of stereochemistry at C-4 in the Buxus alkaloids, suggested by 13C chemical shift considerations,22 has been confirmed by X-ray analysis of the derivative (18) of cyclobuxidine F.23 Assignments of the 13C resonances of a series of cycloartanes have been reported.24... 

The steroidal alkaloids have a nucleus based on 21, 24, or 27 carbon atoms (Fig. 44). The C21 alkaloids are pregnane-derived with nitrogen inserted at C-3, at C-20, or at both positions. They are characteristic of the Apocynaceae Funtumia and Holarrhena species) and the Buxaceae Buxus species). The Buxaceae also produces C24 alkaloids based on the cycloartane skeleton. The most interesting alkaloids are those in the Solanaceae and the Liliaceae. These are C27 alkaloids, and examples include solasodine and solanidine many derivatives are glycosylated. The alkaloids from the Liliaceae, such as veratramine of the white hellebore (Veratrum album), were formerly used for cardiac... 

Triterpenes not belonging to cycloartane series, as a-amyrin and P-amyrin, have been isolated from Aglycyphyllos [165]. From A. complanatus has been identified a new /i-coumaroyl derivative, named 11-0-/ -coumaroylnepecticyn, Fig. (3) [98,272]. 

Taxonomy Cycloartane Glycosides Cimicifuga simplex Ranunculaceae) [1]. Glycoside was obtained as an inseparable mixture with A -derivative. 

The 4a-monomethyl- (II) and 4,4-demethyl-derivatives (III), which are themselves products of partial demethylation, are biogenetically related to cycloartane triterpenoids. 

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