The Assignment of the Absolute Configuration of C-22 Chiral Center in the Aglycones of Triterpene Glycosides from the Sea Cucumber Cladolabes schmeltzii and Chemical Transformations of Cladoloside C

Abstract

The absolute R-configuration of the C-22 chiral center in cladoloside C (1) and therefore in all related glycosides isolated from the sea cucumber Cladolabes schmeltzii has been assigned by Mosher ' s method. Some chemical transformations of the native glycoside 1 were carried out to apply this method. This resulted in the isolation and elucidation of chemical structures of progenin 2 and artefact aglycones 3 and 4, obtained from 1 and assignment of the absolute R-configuration of C-22 in the progenin 2. The coincidence of C-22 configurations in the studied compounds with those of the earlier known lanostane-type aglycone of frondoside C and holostane-type aglycone of cladoloside C (1) confirms the generic biosynthetic pathways to different types of sea cucumber glycoside aglycones. It suggests the same R-configuration of C-22 chiral centers in all the sea cucumber glycosides having C-22 functionalities.

Nine New Triterpene Glycosides, Magnumosides A1–A4, B1, B2, C1, C2 and C4, from the Vietnamese Sea Cucumber Neothyonidium (=Massinium) magnum: Structures and Activities against Tumor Cells Independently and in Synergy with Radioactive Irradiation

“…Indeed, the signals at δ(C) 182.6 (C(18)), 80.1 (C(16)), 62.2 (C(17)) as well as at δ(H) 5.12 (brs, H(16)) and 2.72 (s, H(17)) confirmed the presence of an 18(16)-lactone moiety, the signals at δ(C) 122.3 (C(7)) and 147.6 (C(8)) with corresponding proton signal at δ(H) 5.55–5.57 (m, H(7)) demonstrated the presence of 7(8)-double bond. However the signal of C(20) was high-shifted to δ(C) 71.3 when compared with that of 1 and was close to those of progenins obtained from cladoloside C by its alkaline treatment and having the identical to each other aglycone nuclei with hydroxylated C(20) position and non-shortened side chains [ 25 ]. The signals corresponding to the side chain of 2 formed the isolated spin system in the 1 H, 1 H-COSY spectrum ( Figure 2 ) from H(22) to H(24), indicating the latter signal was down-shifted to δ(H) 4.33 (brt, J = 6.0 Hz, H(24)) due to hydroxylation of this position and the multiplicity of the signal showed its vicinity to quaternary carbon C(25).…”

“…The aglycone of magnumosides B 1 ( 5 ) and C 1 ( 7 ) with 23(24)-double bond and 20,25-hydroxyls is obviously could be the precursor of the unusual aglycone of magnumoside A 1 ( 1 ) with 20(24)-epoxy-25-hydroxy-fragment. The similar conversion of the aglycone having a linear side chain with a double bond and hydroxyl group to the aglycone having epoxy-group was observed in the process of obtaining the genins with 18(16)-lactone moieties by chemical transformations of the holostane aglycone of cladoloside C [ 25 ]. It was considered as a biomimetic reaction, modeling the biosynthetic process in the glycoside aglycones.…”

Magnumosides B3, B4 and C3, Mono- and Disulfated Triterpene Tetraosides from the Vietnamese Sea Cucumber Neothyonidium (= Massinium) magnum

“…The sea cucumber Neothyonidium (=Massinium) magnum, collected in shallow waters near Vietnam shore contained very complicated mixture of the glycosides. As continuation of the investigations of chemical composition of this species herein we report the isolation and structural elucidation of four new sulfated triterpene olygoglycosides, magnumosides B 3 (1), B 4 (2) and C 3 (3).…”

“…The 1 H and 13 C NMR spectra of carbohydrate parts of magnumosides B 3 (1) and B 4 (2) were coincident to each other and to those of magnumosides B 1 and B 2 indicating the identity of carbohydrate chains of these glycosides [1]. The presence of four characteristic doublets at  H 4.65-5.21 (J = 7.3-8.0 Hz) in the 1 H NMR spectra of the carbohydrate chains of 1, 2 correlated by the HSQC spectra with the signals of anomeric carbons at  C 104.…”

“…The cytotoxic activities of magnumosides B 3 (1), B 4 (2) and C 3 (3) against mouse spleenocytes and ascite form of mouse Ehrlich carcinoma cells as well as hemolytic action against mouse erythrocytes have been studied ( Table 5). The sensitivity of the cells to the action of the glycosides decreased in the row: erythrocytes  spleenocytes  Ehrlich carcinoma cells.…”