Cyclization into Hydrindanes Using Samarium Diiodide: Stereochemical Features Depending on the Protecting Group.

Monocyclic compounds bearing ketone and enone moieties in the same molecule can be cyclized to bicyclic compounds initiated by samarium diiodide. The stereochemistry of the products depended on the reaction conditions and also the protecting group of the hydroxy group existed in the molecule. A cyclization mechanism-is discussed.

Synthesis of chiral hexasubstituted cyclohexanediol, a key intermediate for the synthesis of verticillol, from (+)-dihydrocarvone; attempted cyclization to 12-membered carbocycle in verticillol using RCM reaction.

A cyclohexane derivative with three chiral centers, a key intermediate for the synthesis of a diterpene verticillol, was prepared starting from (+)-dihydrocarvone. A further challenge to cyclize to a 12-membered carbocycle was attempted, although the products were dimeric derivatives presumably due to an undesirable conformation of the substrate.

Cyclizations producing hydrindanones with two methyl groups at the juncture positions mediated by samarium diiodide and electrolysis.

One-electron reductive intramolecular cyclization of enones with ketones or aldehydes mediated by samarium diiodide and electrolysis to afford cis-trimethyl- hydrindanolones. The reactions gave selectivities ranging from 1:1 to 100:0 depending on the conditions.

First direct evidence of radical intermediates in samarium diiodide induced cyclization by ESR spectra.

The mechanism of samarium diiodide (SmI(2))-induced cyclization of α,ß-unsaturated esters and ketones to bicyclic compounds was examined using ESR spectroscopy. This is the first report of direct evidence of the radical intermediates in the SmI(2) reaction. The preferential reduction of the α,ß-unsaturated carbonyl part in some substrates should be recognized as a main route.

Sesquiterpenoids isolated from Eupatorium glehnii. Isolation of guaiaglehnin A, structure revision of Hiyodorilactone B, and genetic comparison.

A new sesquiterpenoid substituted with unsaturated ester, guaiaglehnin A (1), along with 15 previously known compounds, were isolated from the methanol extract of the terrestrial part of Eupatorium glehnii (Compositae) collected in Nagano Prefecture, Japan, the results of which supported the previous study by Takahashi et al. The chemical constituents of E. glehnii collected in Nagano Prefecture and those collected in Tokushima or Hokkaido are quite different, depending on collection site, although the species are identical. The base sequences of three different samples were identical. Diversity in the chemical components was detected, though no diversity existed in the DNA sequence. In this study, eupasimplicin A (2) was also isolated, whose presence in the extract of E. chinense simplicifolium was recorded but not in an article. The side chain geometry of hiyodorilactone B (5) was revised to be E.

Chemical and genetic diversity of Ligularia vellerea in Yunnan, China.

Intra-specific diversity in Liularia vellerea growing in the northwestern to central Yunnan province of China was studied by chemical and genetic approaches. Samples collected in the Jianchuan, Lijiang, and Zhongdian areas contained 6,15-dioxygenated furanoeremophilanes as their major components (type A); whereas samples from the Luguhu area accumulated 1,6-dioxygenated furanoeremophilanes (type B); a sample from near Kunming, however, contained 6,15-dioxygenated eremophilanolides (type C). 11 beta H- and 11 alpha H-6 beta-angeloyloxy-15-carboxyeremophil-7-en-12,8-olides (eremofarfugins D and E) were also isolated and their structures were determined. A correlation between the composition and the DNA sequence was observed in the ITSs.

Isomerization reactions of allylic alcohols into ketones with the Grubbs reagent.

Allylic alcohols were isomerized into ketones by the action of the Grubbs reagent. Some model alcohols were prepared and tested under similar conditions to reveal that less substituted alkenes rearrange more easily. More hindered alcohols are stable under these conditions, however, the simple allylic alcohols tend to isomerize producing ethyl ketone and the corresponding degraded methyl ketone.

[6-endo-trig mode cyclization to a hydrindanone using samarium (II) iodide].

Samarium (II) iodide has been employed to promote the vinylogous pinacol coupling reaction of aldehyde to alpha, beta-unsaturated ketones. The diastereoselectivity of 6-endo-trig mode products was changed by the addition of a proton source and/or HMPA and by the reaction temperature. The stereochemistry of the hydrindanone was controlled by the coordinated samarium species, resulting in the cis-orientation in respect of the hydroxyl group at C-4 and the juncture proton at C-3a under mild reaction conditions. Coronafacic acid has been synthesized from a hydrindanone prepared by the cyclization reaction of the enone-aldehyde with samarium (II) iodide.

Seven germacranolides, eupaglehnins A, B, C, D, E, and F, and 2alpha-acetoxyepitulipinolide from Eupatorium glehni.

Four new germacrane-type sesquiterpenoids with unsaturated acids as esters at the 8-position, two chlorine atom-containing lactones, 2alpha-acetoxyepitulipinolide, and 12 previously known compounds have been isolated from the MeOH extract of Eupatorium glehni (Compositae) and their structures have been determined on the basis of spectral data analyses.

Total synthesis and absolute configuration of liverwort diterpenes, (-)-13(15)E,16E-3beta,4beta-epoxy-18-hydroxysphenoloba-13(15),16-diene and (-)-13(15)Z,16E-3beta,4beta-Epoxy-18-hydroxysphenoloba-13(15),16-diene, by use of the ring closing metathesis reaction applied to seven-membered carbocycles with a trisubstituted double bond.

Seven-membered cyclic compounds possessing trisubstituted double bonds have been effectively constructed employing the Grubbs catalyst to effect olefin metathesis. The keto ester does not undergo cyclization; however, alcohols protected by the silyl groups smoothly cyclized into seven-membered compounds. The product was successfully converted to (-)-13(15)E,16E-3beta,4beta-epoxy-18-hydroxysphenoloba-13(15),16-diene and (-)-13(15)Z,16E-3beta,4beta-epoxy-18-hydroxysphenoloba-13(15),16-diene, liverwort diterpenes isolated from Anastrophyllum auritum to establish the absolute configuration.