M. S. Torre, C. Masoller, and Paul Mandel Instituto de Fı́sica ‘‘Arroyo Seco,’’ UNCPBA Pinto 399 (7000) Tandil, Argentina Instituto de Fı́sica, Facultad de Ciencias, Universidad de la República, Igua 4225, Montevideo 11400, Uruguay Université Libre de Bruxelles, Optique Nonlinéaire Théorique, Campus Plaine Code Postale 231, B-1050 Bruxelles, Belgium ~Received 22 March 2002, revised manuscript rec...

Phytochemical investigation on the fruits of Pieris formosa resulted in the isolation of three new highly acylated 3,4-seco-grayanane diterpenoids, pierisformotoxins E-G (1-3). Their structures were elucidated on the basis of extensive spectroscopic analysis, including 1D-, 2D-NMR, electrospray ionization-mass spectra (ESI-MS) and high resolution (HR)-MS.

Marine brown alga Dictyota dichotoma (Dictyotaceae) collected from the Karachi coast of the Arabian Sea has yielded three new C-16 oxidized seco-dolastanes (diterpenoids) named dichotenol-A, B and C. Their structures have been characterized with the aid of 2D-NMR spectroscopic techniques.

Two new 3,4-seco-cycloartane triterpenes, named sootepins H (1) and I (2), were isolated from the ethyl acetate extract of the leaves and twigs of Gardenia sootepensis. Their structures were elucidated on the basis of 1D- and 2D-nuclear magnetic resonance (NMR) analysis, as well as high-resolution mass spectrometry (HR-MS), infrared (IR), and ultra violet (UV).

An effective two step transformation of oridonin to 15,16-seco-ent-kaurane skeleton is reported. We also achieved the conversion of one intermediate to natural product rubescensin S and revised its structure as a 13S configuration although 13R is reported in the literature.

Five new glycosides of 14,15-seco- and 13,14:15-diseco-type pregnanes, including a new pregnane, 2 alpha-hydroxyhirundigenin, were isolated, in addition to one known glycoside, cynatratoside B, from the roots of Tylophora tanakae Maxim. Their structures were elucidated by spectral and chemical means.

Three new 15,16-seco-cycloartane glycosides, which were constructed by a C-C bond cleavage in the D ring, have been isolated from Cimicifuga Rhizome for the first time. Their structures were determined by the use of 2D NMR techniques and chemical evidence.

Isolation and structure elucidation of six new divergolides reveal unusual ansamycin diversification reactions including formation of the unusual isobutenyl side chain from a branched polyketide synthase extender unit, azepinone ring closure, macrolide ring contraction and formation of a seco variant by a neighboring group-assisted decarboxylation.

María-Isabel Sánchez-Segura Antonio de Amescua Seco Juan-José Cuadrado Escuela Politécnica Superior Universidad Carlos III de Madrid Avda. Universidad, 30, Leganes 28911, Madrid, Spain (+34) 91 624 91 04 {misanche; amescua; cuadrado}@inf.uc3m.es Angélica de Antonio Facultad de Informática Universidad Politécnica de Madrid Campus de Montegancedo s/n 28660 Boadilla del Monte, Madrid, Spain (+34) ...

The aconitine-type alkaloids talatisamine (1), 8,14-diacetyltalatisamine (11), and compound 3, the lycoctonine-type alkaloid deltaline (5), and the 7,17-seco C(19)-diterpenoid alkaloids 7 and 9 were treated with HBr-glacial acetic acid to give useful O-demethylated derivatives 2, 2, 4, 6, 8, and 10 respectively in good to high yields (49-90%).