Cyclization and rearrangement of diterpenoids. III. Synthesis of isoagatholactone and methyl spongia-13(16),-14-dien-19-oate

The synthesis of isoagatholactone has been effected by the successive oxidation of (14R)-isoagath-12-en-15-ol with selenium dioxide and manganese dioxide. Methyl spongia-13(16),14-dien-19-oate has been obtained by the cyclization of methyl lambertianate with 100% sulfuric or fluorosulfonic acid.Institute of Chemistry, Academy of Sciences of the Moldavian SSR, Kichinev. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 725–731, November–December, 1984.     

Cyclization and rearrangement of diterpenoids. IV. Synthesis of Δ12- and Δ13(14)-iso-20-deoxyluteones

Chemistry of Natural Compounds - Δ12- and Δ13(14)-Iso-20-deoxyluteones have been synthesized from 13E- and 13Z-bicyclogeranylgeranylacetones. The latter were reduced to the corresponding...     

Total syntheses of (-)-methyl atis-16-en-19-oate, (-)-methyl kaur-16-en-19-oate, and (-)-methyl trachyloban-19-oate by a combination of palladium-catalyzed cycloalkenylation and homoallyl-homoallyl radical rearrangement

Asymmetric total syntheses of (-)-methyl atis-16-en-19-oate (1c), (-)-methyl kaur-16-en-19-oate (2c), and (-)-methyl trachyloban-19-oate (3c) have been achieved by employing a hybrid strategy of palladium-catalyzed cycloalkenylation and homoallyl-homoallyl radical rearrangement. The common synthetic intermediate 5 was prepared from 2-allylcyclohexanone (4) with 98% ee using d'Angelo's asymmetric Michael addition. A series of functional group modifications in 5 via palladium-catalyzed cycloalkenylation led to (+)-14, which had already been prepared by us as racemate. (-)-Methyl atis-16-ene-19-oate (1c) was generated via homoallyl-homoallyl radical rearrangement. On the other hand, Wolff-Kishner reduction of 18 followed by esterification yielded (-)-methyl kaur-16-en-19-oate (2c) together with (-)-methyl trachyloban-19-oate (3c).     

Cyclization and rearrangement of diterpenoids. II. Cyclization of cis-labda-8,13-dien-15-ol by the complex of titanium tetrachloride with N-methylaniline

It has been shown that the product of the reaction of cis-labda-8,13-dien-15-ol (I) with the complex of TiCl₄ (II) and PhNHCH₃ (III) is (1R,2R,7S,10S,12S,13S)-13-chloro-2,6,6,10,12-pentamethyltetracyclo[10.2.1.0^1,10·0^2,7]eicosane (IV), the formation of which gives information on the transformation of labdane diterpenoids into tetracycloeicosane derivatives. The reduction of (IV) with LiAH₄·CoCl₂ gave the corresponding hydrocarbon. It has been shown that (IV) is formed by the reaction of 13-hydroxy-2,6,6,10,12-pentamethyltetracyclo[10.2.1.0^1,10·0^2,7]eicosane with SOCl₂ and ZnCl₂. The characteristics of its IR, mass and NMR spectra are given.Institute of Chemistry of the Academy of Sciences of the Moldavian SSR, Kishinev. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 318–322, May–June, 1984.     

Synthesis of labda-8(17),13(14)-diene-15,16-olide and 15,16-epoxy-labda-8(17),13(16)-14-triene and their rearrangement to clerodane derivatives

The title compounds 1b and 1c were synthesized from manool. On treatment with either trifluoroacetic acid or formic acid 1b provided in nearly 100% yield 4a with a rearranged labdane skeleton. With sulfuric acid, however, 1b gave solely Δ^8,9-isomer 5. Reduction of 4a with lithium diisobutylaluminum hydride afforded 4b. On treatment with sulfuric acid 4a reverted to 5. Rearrangement of the epoxide 6 with boron trifluoride- etherate led to a complex product mixture from which no pure substance was obtained.     

Study on the tetracyclic diterpenoids 4.The solvolysis of methyl 14-β-mesyloxy-ent-kaur-15-en-19-oate

Grandiflorenic acid(1),possessing potent contragestational activity,is an ent-kauranediterpenoid.It has been isolated from Mexical medicinal plant zoapatle(Montanoa tomento)In connection with our synthetic work on ent-kaurane diterpenoids,we are interested in theconversion of stevioside(2)occurred abundantly in Stevia rebaudiana into grandiflorenic acid     

Asymmetric synthesis of methyl (-)-13-oxo-15,16-dinorlabda-8(17),11E-dien-19-oate, methyl ester of a potent suppressor toward carcinogenic promotor

Asymmetric synthesis of methyl ester (4) of (-)-13-oxo-15,16-dinorlabda-8(17),11E-dien-19-oic acid (1), which exhibited the most potent activity for the prevention of incipient carcinogenesis among the isolated diterpenes from Thuja standishii and its related plants, was achieved by using methyl (-)-1,4a-dimethyl-5-oxodecahydronaphthalene-1-carboxylate (5) as a strating material, which was easily prepared on gram scale by baker's yeast-catalyzed asymmetric reduction.     

Synthesis of (+)-podocarp-8(14)-en-13-one and methyl-(+)-13-oxo-podocarp-8(14)-en-18-oate from abietic acid

An efficient method for the preparation of (+)-podocarp-8(14)-en-13-one 6 and methyl-(+)-13-oxo-podocarp-8(14)-en-18-oate 8 from abietic acid is described.     

A Formal Total Synthesis of (+)-Methyl Trachyloban-18-oate and (+)-Methyl 16-Oxo-17-norkauran-18-oate: Regio- and Diastereoselective Preparation of Methyl (13S)-13-Hydroxyisoatisiren-18-oate from (−)-Abietic Acid

A novel preparation of methyl (13S)-13-hydroxyisoatisiren-18-oate ( 4 ), a key-intermediate in a synthesis of (+)-methyl trachyloban-18-oate ((+)- 1 ), from (?)-abietic acid, is described. Since (?)- 1 has been previously converted into (?)-methyl 16-oxo-17-norkauran-18-oate ((?)- 16 ), our preparation of 4 constitutes also a formal total synthesis, from (?)-abietic acid, of (+)- 16 . Key steps in this approach were the allene photoaddition to podocarp-8(14)-en-13-one ( 5 ) and the conversion of the endo-toluene-4-sulfonate 11 into the exo-benzoate 12b .     

Total syntheses of (±)-isoagatholactone and (±)-12α-hydroxyspongia-13(16),14-dien

(±)-Isoagatholactone $\text{1}$ and (±)-12α-hydroxyspongia-13(16),14-dien $\text{2b}$, a fundamental skeleton of spongiadiol $\text{2a}$ and its congeners, have been synthesized from (±)-labda-8(20),13-dien-15-oic acid $\text{3}$.     

1H and 13C NMR spectral assignments and conformational analysis of 14 19-nor-neoclerodane diterpenoids

Unambiguous and complete assignments of 1H and 13C NMR chemical shifts for 14 19-nor-neoclerodane diterpenoids, nine of them isolated from natural sources and five other synthetic derivatives, are presented. The assignments are based on 2D shift-correlated (1H,1H-COSY, 1H,13C-gHSQC and 1H,13C-gHMBC) and NOE experiments. The conformations of rings A and B of these compounds are supported by the 3J(H,H) values and they agree with the low-energy conformations obtained by semi-empirical calculations. Moreover, the data obtained in this work for 2-acetoxyteucvidin and a semisynthetic 18-aldehyde derivative indicate that the configuration at C-2 of the former and at C-10 of the latter must be reversed with respect to those reported previously.     

A total synthesis of (±)-gibberellin A12 via methyl (±)-7,16-dioxo-17-norkauran-19-oate

A formal total synthesis of (±)-gibberellin A₁₂ (1) was achieved by employing methyl (±)-7,16-dioxo-17-norkauran-19-oate (13) as a relay compound.     

四环二萜的合成研究 5.对映贝壳杉-16-烯-19酸的合成

本文报道了一条从易得的甜叶菊苷出发经二次骨架重排合成了对映贝壳杉-16-烯-19-酸及其异构体.从甜叶菊苷合成对映贝壳杉-16-烯-19-酸的九步反应总产率为9%而合成对映贝壳杉-15-烯-19-酸的九步反应总产率炒17%.     

Synthesis of 2,11-dioxo-norolean A(1)-12,18(19)-dien-30-oic acid

A new A-noroleanane triterpenoid with an altered pentacyclic skeleton of 2,11-dioxo-norolean A(1)-12,18(19)dien-30-oic acid based on 18,19-dehydroglycyrrhetic acid was synthesized.     

Synthesis and rearrangement of 13-thiaprostanoids

Thiaprostanoids 13 were prepared by conjugate addition of mercaptane 6 to cyclopentenones 12 and 20. Novel rearrangements of these compounds to 14 and 15 were interpreted as enolate induced [1,5]-sigmatropic shift on the corresponding dehydration products 16. Preparation of the various substrates and structural elucidation of new products are described.