Conrad Pascual

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.

Diterpenoids from Ajuga chamaepitys: Two neo-clerodane derivatives

Abstract From the whole plant of Ajuga chamaepitys two new neo -clerodane diterpenoids, ajugapitin and its dihydro derivative, have been isolated. Their

Ursane and oleanane triterpenoids from Salvia argentea

Abstract From the aerial parts of Salvia argentea four new ursene and two new oleanene triteipenoids have been isolated, together with the already known ursolic and oleanolic acids. The structures of the new substances were established by chemical and spectroscopic means.

Neo-clerodane diterpenoids from Teucrium lanigerum

Abstract From the aerial part of Teucrium lanigerum , six new neo-clerodane diterpenoids, 7,8-dehydroeriocephalin, teulanigeral, teulanigin, 20-epi-teulanigin, teulanigerin and teulanigeridin, have been isolated. The first of these, 7,8-dehydroeriocephalin, is a natural substance, whereas the other compounds were isolated as their acetyl derivatives after acetylation of an inseparable mixture of natural diterpenoids. The structures of these substances were established mainly by spectroscopic means and, in the case of 7,8-dehydroeriocephalin, by partial synthesis from eriocephalin.

Teuscorodin, teuscorodonin and 2-hydroxyteuscorolide, neo-clerodane diterpenoids from teucrium scorodonia

Abstract From the aerial part of Teucrium scorodonia (Labiatae) three new neo-clerodane diterpenoids have been isolated. Their structures, (12 S )-15,16-epoxy-2α-hydroxy-19-nor-neo-clerodane-4,6,13(16),14-tetraene-18,6:20,12-diolide (2-hydroxyteuscorolide), (12 S ,18 R )-15,16-epoxy-6-keto-neo-clerodane-13(16),14-dien-20,12-olide-18,19-hemiacetal (teuscorodin) and (12 S )-15,16-epoxy-19-hydroxy-neo-clerodane-3,13(16),14-triene-18,6β:20,12-diolide (teuscorodonin), have been established by chemical and spectroscopic means and by correlation with known products.

The correct structure of salvifaricin a cis neo-clerodane diterpenoid from Salvia farinacea

Abstract The structure and absolute configuration of salvifaricin, a neo-clerodane diterpenoid isolated from Salvia farinacea , have been firmly established by extensive NOE experiments and by chemical correlation with salvifarin, another diterpenoid isolated from the same source. These results slightly modify the structure previously assigned to the compound.

Neo-clerodane diterpenoids from Teucrium salviastrum

Abstract From the aerial parts of Teucrium salviastrum six new neo-clerodane diterpenoids, teusalvins A–F, have been isolated, together with the previously known diterpenes teucvidin teucroxide. The structures of teusalvins A [15,16-epoxy-2,6-diketo-neo- cleroda-13(16),14-dien-20,12S-olide-18R19-hemiacetal], B [15,16-epoxy-2β-hydroxy-6-keto-neo-cleroda-13(16),14-dien-20,12S-olide-18R,19-hemiacetal], C [15,16-epoxy-6β,18,19-trihydroxy-neo-cleroda- 3,13(16),14-trien-20,12R-olide], D [15,16-epoxy-2β,6β,18,19-tetrahydroxy-neo-cleroda-3,13(16),14-trien-20,12S-olide], E [15,16-epoxy-2β,6β,12S,18-tetrahydroxy-neo-cleroda-3,13(16),14-trien-20,19-olide] and F [15,16; 19,2α-diepoxy-6β,8-dihydroxy-neo-cleroda-3,13(16),14-trien-20,12S-olide] were established mainly by spectroscopic means and, in the case of teusalvin F, by X-ray diffraction.

Preleosibirin, a prefuranic labdane diterpene from ballota nigra subsp. foetida

Abstract From the aerial parts of Ballota nigra subsp. foetida a new prefuranic labdane diterpene, preleosibirin, has been isolated. Its structure was established by spectroscopic means and by correlation with the previously known diterpenoid leosibirin.

6-epiteucrin A, a neo-clerodane diterpenoid from Teucrium chamaedrys

Abstract From the aerial part of Teucrium chamaedrys a new 19-nor-neo-clerodane diterpenoid, 6-epiteucrin A, has been isolated, besides the previously known diterpenoids teuflin, teuflidin, teucrin E and teuchamaedryn B. The structure of 6-epiteucrin A, (12S)-15,16-epoxy-7α-hydroxy-19-nor-neo-cleroda-4,13(16),14-triene-18,6β: 20,12-diolide, was established by spectroscopic means and by correlation with teucrin A.

New compounds from . X-ray crystal and molecular structures of anamarine

Abstract The structure (including absolute stereochemistry) of olguine, an unsaturated lactone isolated from an unclassified Hyptis species, has been established by spectroscopic and X-ray analysis.