Structure of thalicmidine
The alkaloid thalicmidine isolated from the roots of Thalictrum minus by S. Yu. Yunusov and N. N. Pmgressov [1] contains three methoxy groups and one hydroxy group (broad band in the IR spectrum at 3200-3500 cm-~). The UV spectrum of thalicmidine has three maxima at 220, 280, and 305 mg (tog e 4.52, 4.12, 4.12), which are characteristic for 2, 3, 5, 6-tetrasubstituted aporphins [2]. Methylation of thalicmidine has given glaucine (Ia) and oxidation has yielded m-hemipinic acid, Consequently, the hydroxy group must occupy position 5 or 6 [3, 4]. Since thalicmidine is not identical with glaueentrine, only position 6 remains possible for the hydroxy group (Ib).
Scutellarin fromSorbaria sorbifolium
By column chromatography on a column of polyamide sorbent (elution with 40% ethanol) we have isolated from the leaves of Sorbaria sorbifolium (Ural falsespirea) in the Khekhtsirskii reserve (Kharabov territory) a substance ( I )o f f lavonoid nature, C21H~O20 • H20 with mp 218-220" C, kma x g35, 286 m/£ The hydrolysis of substance I with 10% sulfuric acid in the presence of acetic acid yielded an aglycone which, from its melting point, Rf value and the absence of a depression of the mel t ing point in a mixture with an authentic sample, was identified as sentellarein. Glucuronic acid was detected in the mother liquor after the separation of the aglyeone and neutralization with alkal i to pH 5 by paper chromatography. On the basis of the constants given, the products of hydrolysis, and a direct comparison with an authentic sample, substance I was identified as scutellarin (scutellarein 7-glyeuronide) [1]. The sample of scutellarin was obtained from V. A. Bandyukova (Pyatigorsk).
Calyculins and Related Marine Natural Products as Serine-Threonine Protein Phosphatase PP1 and PP2A Inhibitors and Total Syntheses of Calyculin A, B, and C
Calyculins, highly cytotoxic polyketides, originally isolated from the marine sponge Discodermia calyx by Fusetani and co-workers, belong to the lithistid sponges group. These molecules have become interesting targets for cell biologists and synthetic organic chemists. The serine/threonine protein phosphatases play an essential role in the cellular signalling, metabolism, and cell cycle control. Calyculins express potent protein phosphatase 1 and 2A inhibitory activity, and have therefore become valuable tools for cellular biologists studying intracellular processes and their control by reversible phosphorylation. Calyculins might also play an important role in the development of several diseases such as cancer, neurodegenerative diseases, and type 2-diabetes mellitus. The fascinating structures of calyculins have inspired various groups of synthetic organic chemists to develop total syntheses of the most abundant calyculins A and C. However, with fifteen chiral centres, a cyano-capped tetraene unit, a phosphate-bearing spiroketal, an anti, anti, anti dipropionate segment, an α-chiral oxazole, and a trihydroxylated γ-amino acid, calyculins reach versatility that only few natural products can surpass, and truly challenge modern chemists’ asymmetric synthesis skills.