Chemistry of Sponges. 19. Novel Bioactive Metabolites from Hamigera tarangaensis

Abstract

Seven new compounds (1-6 and 10) with a unique carbon skeleton have been isolated from the sponge Hamigera tarangaensis, and the structure of a previously reported metabolite has been revised from 12 to 8. The structures have been assigned from extensive NMR examination. Compounds 3-6 showed moderate in-vitro cytotoxicity against P-388, while 3 showed 100% in-vitro virus inhibition against both the Herpes and Polio viruses, with only slight cytotoxicity.

Palladiumkatalysierte Kreuzkupplungen in der Totalsynthese

“…B. von b-Ketoestern oder Malonaten) am häufigsten als Kohlenstoffnucleophile in der asymmetrischen allylischen Alkylierung eingesetzt werden, [232] ist ein zunehmendes Interesse an anderen Nucleophilen zu verzeichnen. Die Arbeitsgruppe um Trost hat die jüngste Entwicklung von Protokollen für die asymmetrische Alkylierung von KetonEnolaten maßgeblich mitgestaltet [233] und diese außerordent-lich nützliche Nucleophilklasse in der eleganten Synthese von Hamigeran B, einem antiviralen Metaboliten aus dem Meeresschwamm Hamigera tarangaensis, [234] angewendet (290, Schema 52). [235] Die Syntheseroute verlangte die frühe Einführung des methylsubstituierten quartären Stereozentrums; dies gelang durch die asymmetrische allylische Alkylierung Schema 51.…”

Enantiosective synthesis of a substituted cyclopentanone with all-carbon quaternary stereocenter

“…1 However there is a strong demand for the development of effective methods for the asymmetric synthesis of organic compounds containing such structural units which were revealed in a variety of natural compounds and bioactive molecules. In particular, many terpenoids, [1][2][3][4][5] alkaloids 1,6,7 and prostaglandin analogs 8 contain substituted cyclopentane fragments containing such chiral centers. Currently, there are few direct C-C bond formation reactions that have been successfully applied for the construction of all-carbon quaternary stereocenters.…”

α‐Hydroxylation of β‐Dicarbonyl Compounds

“…Among these are antibiotics such as kjellmanianone (1), [1] hamigeran A (3) [2] or doxycycline (4), [3] shown in Scheme 1. a-Acetolactate (2a) and aacetohydroxybutyrate (2b) [4] are the biosynthetic precursors of valine and isoleucine (Scheme 1). Moreover, this functional unit appears in key intermediates in many multi-step reaction sequences, for example, in the synthesis of the Aspidosperma alkaloids 11-demethoxyvindoline (5a) and vindoline (5b).…”