Anna M. Lithgow

Ambergis compounds from labdanolic acid

Abstract Labdanolic acid (Cistus ladaniferus) is transformed into derivatives with amber odor. The strategy used allowed a process in which the oxidative decarboxylation reaction was carried out with the hydroxyl group protected.

Meroterpenes from Cystoseira usneoides II

Abstract Two new meroterpenes, usneoidols Z and E, have been isolated from the brown seaweed Cystoseira usneoides . Their structures were established by means of 2D NMR experiments: 1 H/ 1 H (COSY) and 1 H/ 13 C one bond and long range (HCCORR) correlations. Both compounds exhibit antitumoural and antiviral activities.

CHIRAL RECOGNITION OF TARTARIC ACID DERIVATIVES WITH CHROMENONE-BENZOXAZOLE RECEPTORS AND A SPIROBIFLUORENE SPACER

Abstract The combination of a spirobifluorene spacer with two chromenone-amino-benzoxazole binding arms affords a chiral cleft type receptor. Due to the strong chiral recognition, resolution of the receptor racemic mixture can be achieved by means of a silica gel TLC plate impregnated with optically pure dibenzoyl tartaric acid. Slow complex formation on the 1 H-NMR scale with this host at −10°C allows observation of different signals for free and complex guests in 1 H-NMR.

Chemistry of zamoranic acid. Part V Homochiral semisyntheses of active drimanes: Pereniporin B, polygodial and warburganal

Abstract Methyl 14,15-dinor-13-oxo-7-labden-15-oate was obtained from acid zamoranic acid methyl ester. The former by photochemical cleavage yielded methyl 7,9(11)-drimadien-12-oate, whose chemoselective epoxidation afforded methyl 9α,11-epoxy-7-drimen-12-oate, which is the key synthetic precursor for pereniporin B, polygodial and warbuganal.

Meroterpenes fromCystoseira usneoides

Abstract Two new meroterpenes have been isolated from the brown seaweed Cystoseira usneoides usneoidone E and usneoidone Z. Their structures were established mainly by means of 2D NMR experiments: 1 H/ 1 H (COSY) and 1 H/ 13 C one bond and long range (HCCORR) correlations. Both compounds exhibit antitumoural and antiviral activities.

Chemistry of zamoranic acid. Part IX homochiral synthesis of polygodial and warburganal from 17-acetoxy-7-labden-15-ol

Abstract 14,15-di nor -17-acetoxy-7-labden-13-one, 4 was prepared from zamoranic acid methyl ester 5 . Photochemical cleavage of 4 gave 12-acetoxy-7,9(11)-drimadiene, 3 , in 75% overall yield. The chemo- and diastereoselective epoxidation of 3 afforded 12-acetoxy-9α and 9β(11)-epoxy-7-drimene, 17 and 18 in 4:1 ratio. Ring-opening of 17 (or the mixture 17 18 ) using BF 3 ·Et 2 O or ring-opening of the mixture 17 18 lead to the synthetic precursor of polygodial: (9 R )-12-acetoxy-drimen-11-al, 20 , with a 90% diastereoisomeric excess. The chemo- and diastereoselective cis -hydroxylation of diene 3 led to the synthetic precursor of warburganal 9α,11,12-trihydroxy-7-drimene, 29 with 47% yield. Polygodial and warburganal were prepared from zamoranic acid methyl ester in 55 and 27% overall yield, respectively.

Two New Diterpene Isocyanides from a Sponge of the Family Adocidae

10-Isothiocyanatobiflora-4,15-diene (4) and 7-isocyanoneoamphilecta-11,15-diene (5) have been isolated together with known amphilectene diterpenes from a sponge belonging to the family Adocidae. The structures of 4 and 5 were determined by spectroscopic methods and X-ray respectively.

Terpenoids and other constituents of Eucalyptus globulus

The wood of Eucalyptus globulus contains several pentacyclic diterpenes with oleane, ursane and lupane skeleta. In addition to the well known compounds β-amyrin, erythrodiol, uvaol, acetyloleanolic, acetylbetulinic, acetylursolic, betulinic, ursolic, 23-hydroxyursolic and trans-p-methoxycinnamoyloxy-ursolic acids, three new triterpenoids have been isolated: methyl cis-p-methoxycinnamoyloxyoleanolate, methyl cis-p-methoxycinnamoyloxyursolate and methyl 11α-methoxy-3-acetoxyursolate.

Chemistry of 7-labden-3β,15-diol (I): homochiral synthesis of fregenedadiol

Abstract 7-labden-3β,15-diol was transformed into its diacetyl or dimethoxy derivatives. By double bond isomerization, allylic oxidation and dehydrogenation the diacetyl derivative was transformed into a dienone that was aromatized with good yield by methyl loss to afford 3β,15-diacetoxy-20-nor-5,7,9-labdatrien-7-ol. An analog procedure was used to transform the dimethoxy derivative into 3β,15-dimethoxy-20-nor-5,7,9-labdatrien-7-ol. The triflate of the latter was transformed by a cross-coupling reaction into fregenedadiol dimethyl ether that was demethylated to afford fregenedadiol.

Side-chain migration reactions and ring B aromatization in labdanes: scope and limitations. Synthesis of isofregenedane type tetrahydronaphthalenic diterpenes

Abstract The reaction of bicyclic diterpenes with an allylic oxygenated function or an equivalent functionality on ring B in the presence of I2/benzene afforded a simple and rapid synthesis of tetrahydronaphthalenic diterpenes of the isofregenedane class.