María C. de la Torre

The C-12 and C-20 configurations of some neo-clerodane diterpenoids isolated from Teucrium species

Abstract A convenient and conclusive method for determining the C-12 stereochemistry of neo-clerodan-20,12-olide derivatives, even when only one epimer is available, is by 1 H NMR NOE measurements. The C-12 configuration of 26 neo-clerodane diterpenoids isolated from Teucrium species has been re-examined by using this type of experiment. The results indicated that all the previous assignments were correct, except for teupyreinin, where the previously assigned C-12( S ) configuration must be amended to C-12( R ). This was confirmed by chemical transformations and additional 1 H and 13 C NMR studies. Furthermore, the NOE experiments allowed the assignment of a C-20( S ) configuration for teuflavin, the structure of which had previously been reported without this feature, and indicated that the previously assigned C-20( S ) configuration for teupyreinidin must be amended to C-20( R ). The validity of using NOE experiments to establish the C-12 and C-20 configurations in these neo-clerodane derivatives has been confirmed by applying it to compounds whose structure had already firmly established by X-ray diffraction analyses.

An antimicrobial abietane from the root of Plectranthus hereroensis.

A new abietane diterpene, 16-acetoxy-7 alpha, 12-dihydroxy-8,12-abietadiene-11,14-dione, has been isolated from the acetone extract of the root of Plectranthus hereroensis and its structure established by spectroscopic means. This compound showed antibacterial activity against Staphylococcus aureus and Vibrio cholerae, and antiviral activity against Herpes simplex type II.

Guaiane sesquiterpenes from Teucrium leucocladum

Abstract Three guaiane derivatives have been isolated from the aerial parts of Teucrium leucocladum . Their structures [1α,5β-guai-10(14)-ene-4β,6β-diol (teucladiol), 1α,5β-guaiane-4β,6β,10α-triol (teuclatriol) and 1α,5β-guaiane-4β,6β,10β-triol (10-epiteuclatriol)] were established by 1 H and 13 C NMR spectroscopic studies and by comparison with closely related compounds. In addition, the already known neo -clerodane diterpene montanin C has also been isolated from the same source.

Scutalpin a, a neo-clerodane diterpene from scutellaria alpina

Abstract A new neo -clerodane diterpenoid, scutalpin A, has been isolated from Scutellaria alpina . The structure of scutalpin A [7 β ,19-diacetoxy-6 α -(2′ S )-methylbutyryloxy-4 α ,18; 8 β ,13 S -diepoxy- neo -clerodan-15,16-olide] was established by spectroscopic methods, including an X-ray diffraction analysis which provided its absolute stereochemistry.

A straightforward synthesis of tetrameric estrone-based macrocycles.

A straightforward approach to macrocycles having four estrone-derived nuclei by the sequential Cu-catalyzed Huisgen azide-alkyne cycloaddition-Glaser-Eglington Cu homocoupling has been developed. Due to its efficiency and simplicity, this sequence is useful for application to different natural product scaffolds.

Platinum-catalysed bisindolylation of allenes: a complementary alternative to gold catalysis.

Pt versus Au: Platinum-catalysed addition of nucleophiles to allenes follows a distinctly different pathway to the process catalysed by gold(I) complexes; the platinum catalyst leads to different products with indoles involving a bisindolylation reaction, whereas gold(I) gives allyl indoles from a single addition (see scheme).

ABIETANE DITERPENOIDS FROM PLECTRANTHUS GRANDIDENTATUS

The acetone extract of the whole plant of Plectranthus grandidentatus provided the already known abietanes royleanone, 6,7-dehydroroyleanone, horminone, 6β-hydroxyroyleanone, 7α-acetoxy-6β-hydroxyroyleanone and the abietane dimers grandidone C, grandidone D and 7-epigrandidone D, together with a mixture of fatty acid esters of 7α-acyloxy-6β,12-dihydroxy-abieta-8,12-diene-11,14-dione. Some of these compounds showed moderate antibacterial activity.

20-nor-abietane and rearranged abietane diterpenoids from the root of Salvia argentea

Abstract From the root of Salvia argentea three new abietane diterpenoids, 1R-hydroxymiltirone, arucadiol and 1-keto-aethiopinone, have been isolated, together with the previously known diterpenes isopimara-8(9),15-diene, salvipisone, ferruginol and aethiopinone. The structures of the new compounds were established by spectroscopic means.

Neo-clerodane insect antifeedants from Scutellaria alpina subsp. javalambrensis

Abstract Seven previously known neo-clerodanes have been isolated from Scutellaria alpina subsp. javalambrensis together with a new diterpenoid, 11-deacetylscutalpin D, whose structure was established as (13 S )-19-acetoxy-4 α ,18:8 β ,13-diepoxy-11 β -hydroxy-6 α -tigloyloxy-neo-clerodan-15,16-olide by chemical and spectroscopic means. The antifeedant activity of some of the isolated diterpenoids (scutalpins B-D) was assessed against larvae of Spodoptera littoralis and one of them (scutalpin C) showed very potent activity.

Rearranged abietane diterpenoids from the root of two Teucrium species

Abstract From the root of Teucrium fruticans , two new rearranged abietane diterpenoids, teuvincenones F and G, have been isolated together with the known diterpene teuvincenone E. The acetone extract of the root of T. polium subsp. expansum yielded three previously known compounds (ferruginol and teuvincenones A and B) and two new 17(15 → 16)- abeo -abietane derivatives (teuvincenones H and I). The structures of the new diterpenoids [12,16-epoxy-11,14-dihydroxy-17(15 → 16), 18(4 → 3)- diabeo -abieta-3,5,8,11,13,15-hexaene-2,7-dione (teuvincenone F), (16 S )-12,16-epoxy-11,14-dihydroxy-17(15 → 16)- abeo -abieta-8,11,13-triene-3,7-dione (teuvincenone G), 12,16-epoxy-6,11,14-trihydroxy-17(15 → 16)- abeo -abieta-5,8,11,13,15-pentaene-3,7-dione (teuvincenone H) and 12,16-epoxy-6-hydroxy-17(15 → 16)- abeo -abieta-5,8,12,15-tetraene-3,7,11,14-tetraone (teuvincenone I)] were established by spectroscopic means and by comparison with closely related compounds.