Radikalische Cyclisierung von Dienen, II. Zur Regio‐ und Stereoselektivität der radikalischen Cyclopentan‐Synthese aus Dienen über Alkenylquecksilbersalze

Weinges, Klaus; Sipos, Wolfgang

doi:10.1002/cber.19881210224

Cited by 9 publications

(4 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A priori, it is difficult to predict the exo/endo selectivity between the two cis isomers: “boat-axial” transition structure C - I provides isoprostanes 1 and 2 , whereas all syn isomers 3 and 4 are expected from “chair-equatorial” transition structure C - II . Closely related model studies suggest that these two pathways are indeed competitive in the absence of overriding steric effects. , So far, 1 is the only isoprostane isolated from plasma and fully characterized. Independent syntheses of 3 and 4 will be useful for ascertaining their presence in biological fluids.…”

Section: Resultsmentioning

confidence: 99%

Enantioselective Synthesis of 12-epi-PGF₂_α and 12,15-diepi-PGF₂_α

Lai

Lee

et al. 1999

J. Org. Chem.

View full text Add to dashboard Cite

An enantioselective synthesis of 12-epi-PGF2 α (3) and 12,15-diepi-PGF2 α (4), PG-like compounds that are probably generated in vivo by nonenzymatic, free-radical-induced peroxidation of arachidonic acid, has been achieved starting from the commercially available Corey lactone (9). The key strategy involves SmI2 reduction of the γ,δ-epoxy-α,β-unsaturated ester 7, followed by in situ trapping with hexanal; subsequent hydrogenation and decarboxylation affords the stereoselective construction of the lower side chain. This new method is expected to provide a convenient access to various PG-like isoprostanes derived from oxidation of arachidonic acid and cis-4,7,10,13,16,19-docosahexaenoic acid.

show abstract

Section: Resultsmentioning

confidence: 99%

Enantioselective Synthesis of 12-epi-PGF₂_α and 12,15-diepi-PGF₂_α

Lai

Lee

et al. 1999

J. Org. Chem.

View full text Add to dashboard Cite

show abstract

“…To a stirred solution of (1,2,2trimethylcyclopentane-1,3-diyl)dimethanol 25 (3.70 g, 21.47 mmol) and triethylamine (7.3 ml, 2.2 mol equivs) in DCM (70 ml) at -10 • C was added dropwise mesyl chloride (3.66 ml, 2.2 mol equivs) in DCM (20 ml) over 20 min. The mixture was stirred at 0 • C for 1 h then at RT overnight.…”

Section: Syntheses (1r3s) -(122 -Trimethylcyclopentane -13 -Diyl)bis(...mentioning

confidence: 99%

Synthesis of (1R,4S,6R)-5,5,6-trimethyl-2-phosphabicyclo[2.2.2]octane and derivatives

2010

View full text Add to dashboard Cite

The novel primary phosphine (1R,3S)-[1,2,2-trimethyl-3-(phosphinomethyl)cyclopentyl]methyl methanesulfonate 3a (or tosylate 3b) has been prepared in three steps from (1R,3S)-camphoric acid with a view to utilising it as a synthon for the preparation of polycyclic phosphines. Efforts to prepare a [3.2.1] bicyclic product by internal cyclisation of 3a or 3b under various conditions were unsuccessful, but heating the neat compound at 140 degrees C for several hours gave the new asymmetric, bicyclic secondary phosphine, (1R,4S,6R)-5,5,6-trimethyl-2-phosphabicyclo[2.2.2]octane (PBO) as its methanesulfonic acid 5a (or p-toluenesulfonic acid 5b) salt. The cyclisation involves a skeletal rearrangement and occurs with high stereoselectivity to generate two new stereogenic carbon centres and a chiral phosphorus atom. The secondary phosphine was obtained after base treatment of 5a/b and several derivatives of the phosphine have been synthesised and characterised. Reaction of two mol equivalents of the borane adduct of PBO with alpha,alpha'-dichloro-ortho-xylene gave the bidentate derivative, o-C(6)H(4)(CH(2)PBO)(2).2BH(3), 12, and ultimately o-C(6)H(4)(CH(2)PBO)(2), 13. Complexes of 13 with Pd(II), Pt(II), Pt(0) and Mo(0) have been prepared and characterised by spectroscopic and analytical methods including single-crystal X-ray structure determinations of cis-Pd{o-C(6)H(4)(CH(2)PBO)(2)}Cl(2), 14, cis-Pt{o-C(6)H(4)(CH(2)PBO)(2)}Cl(2), 15 and Mo(CO)(4){o-C(6)H(4)(CH(2)PBO)(2)} 17.

show abstract

“…The org. phase was worked up as usual, affording 29.92 g (90 %) of 12/12a after FC (hexane/AcOEt 92: 8). IR (CDCI,): 3062~1, 2960s, 2864s, 1735vs, 1470s, 1390s, 1370s, 1245vs, 1061s, 900s.…”

Section: (Ls4r)-4-(bromomethyl)-22-dimethyl-3-methylidenecyclohexanmentioning

confidence: 99%

“…Swern oxidation of 6 afforded aldehyde 7 which was transformed by a Wittig reaction with MePPh,Br into olefin 8. Deprotection of 8 with tetrabutylammonium fluoride (Bu,NF) gave 9, and the reaction with Ac,O afforded acetate 10 in 73 % yield with respect to the starting material 4 [7] [8]. The key step of the synthesis of the optically active end group 3 is the ring enlargement of acetate 10 to the bromocyclohexane derivative 11.…”

mentioning

confidence: 99%

C₄₅‐ and C₅₀‐Carotenoids Part7 Total synthesis of (all‐E,2R,6R,2′R,6′R)‐ and (all‐E,2R,6S,2′R,6′S)‐2,2′‐Bis(4‐hydroxy‐3‐methylbut‐2‐enyl)‐γ,γ‐carotene (sarcinaxanthin)

Lanz

Bartels

Pfander

1997

Helvetica Chimica Acta

View full text Add to dashboard Cite

The synthesis of sarcinaxanthin ((2R,6R,2'R,6R)-1), a symmetrical C,,-carotenoid with two y-end groups, isolated from Surcina lutea and from Ce//ulomonus biazotea as major pigment, was based on the strategy C,, + C,, + C,, = C,, using camphoric acid as starting material for the C,,-end group 3. The key step of the synthesis is a ring enlargement of the cyclopentane derivative 10 with 2,4,4,6-tetrabromocyclohexa-2,5-dien-l-one (TBCO) to give the cyclohexane derivative 11 (Scheme f). The spectroscopic data of the synthetic compound are in full agreement with the data of the isolated product and give the final proof for the (2R,6R,2'R,6'R) chirality of natural sarcinaxanthin.

show abstract

Radikalische Cyclisierung von Dienen, II. Zur Regio‐ und Stereoselektivität der radikalischen Cyclopentan‐Synthese aus Dienen über Alkenylquecksilbersalze

Cited by 9 publications

References 21 publications

Enantioselective Synthesis of 12-epi-PGF₂_α and 12,15-diepi-PGF₂_α

Enantioselective Synthesis of 12-epi-PGF₂_α and 12,15-diepi-PGF₂_α

Synthesis of (1R,4S,6R)-5,5,6-trimethyl-2-phosphabicyclo[2.2.2]octane and derivatives

C₄₅‐ and C₅₀‐Carotenoids Part7 Total synthesis of (all‐E,2R,6R,2′R,6′R)‐ and (all‐E,2R,6S,2′R,6′S)‐2,2′‐Bis(4‐hydroxy‐3‐methylbut‐2‐enyl)‐γ,γ‐carotene (sarcinaxanthin)

Contact Info

Product

Resources

About

Radikalische Cyclisierung von Dienen, II. Zur Regio‐ und Stereoselektivität der radikalischen Cyclopentan‐Synthese aus Dienen über Alkenylquecksilbersalze

Cited by 9 publications

References 21 publications

Enantioselective Synthesis of 12-epi-PGF2α and 12,15-diepi-PGF2α

Enantioselective Synthesis of 12-epi-PGF2α and 12,15-diepi-PGF2α

Synthesis of (1R,4S,6R)-5,5,6-trimethyl-2-phosphabicyclo[2.2.2]octane and derivatives

C45‐ and C50‐Carotenoids Part7 Total synthesis of (all‐E,2R,6R,2′R,6′R)‐ and (all‐E,2R,6S,2′R,6′S)‐2,2′‐Bis(4‐hydroxy‐3‐methylbut‐2‐enyl)‐γ,γ‐carotene (sarcinaxanthin)

Contact Info

Product

Resources

About

Enantioselective Synthesis of 12-epi-PGF₂_α and 12,15-diepi-PGF₂_α

Enantioselective Synthesis of 12-epi-PGF₂_α and 12,15-diepi-PGF₂_α

C₄₅‐ and C₅₀‐Carotenoids Part7 Total synthesis of (all‐E,2R,6R,2′R,6′R)‐ and (all‐E,2R,6S,2′R,6′S)‐2,2′‐Bis(4‐hydroxy‐3‐methylbut‐2‐enyl)‐γ,γ‐carotene (sarcinaxanthin)