Stereoselective method for the synthesis of both olefinic isomers from a single precursor.  Conjugate reduction of .alpha.,.beta.-unsaturated epoxides

Lenox, Ronald S.; Katzenellenbogen, John A.

doi:10.1021/ja00784a073

Cited by 54 publications

(15 citation statements)

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“…In view of the fact that the trisubstituted double bond in 20 is the most electron‐rich one, a selective epoxidation was devised and successfully realized with m ‐CPBA at −20 °C. Thereafter, a direct S N 2′‐type reduction of the resultant epoxide was realized with DIBAL‐H to produce 21 in 52 % yield over three steps from 19 18. Other hydride reagents, such as LiBH 4 and NaBH 4 , gave decreased yields.…”

Section: Resultsmentioning

confidence: 99%

Collective Total Synthesis of Englerin A and B, Orientalol E and F, and Oxyphyllol: Application of the Organocatalytic [4+3] Cycloaddition Reaction

Wang

Chen

Sun

et al. 2013

Chemistry A European J

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The concise collective total synthesis of englerin A and B, orientalol E and F, and oxyphyllol has been accomplished in 10-15 steps, with the total synthesis of orientalol E and oxyphyllol being achieved for the first time. The success obtained was enabled by the realization of the [4+3] cycloaddition reaction of 9 and 10. Other features of the synthesis include 1) the intramolecular Heck reaction to access the azulene core, 2) the epoxidation-S(N)2' reduction sequence to access the allylic alcohol, 3) the efficient regioselective and stereoselective formal hydration of the bridging C=C bond in the synthesis of englerins, and 4) the late-stage chemo- and stereoselective C-H oxidation in the synthesis of orientalol E. The total synthesis of these natural products has enabled the structural revision of oxyphyllol and established the absolute stereochemical features of the organocatalytic [4+3] cycloaddition reaction. The identification of 5 as the natural product oxyphyllol, the success in converting 5 to orientalol E, along with the fact that englerins and oxyphyllol were isolated from plants of the same genus Phyllanthus gives support to our proposed biosynthetic pathways. This work may enable detailed biological evaluations of these natural products and their analogues and derivatives, especially of their potential in the fight against renal cell carcinoma (RCC).

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Section: Resultsmentioning

confidence: 99%

Collective Total Synthesis of Englerin A and B, Orientalol E and F, and Oxyphyllol: Application of the Organocatalytic [4+3] Cycloaddition Reaction

Wang

Chen

Sun

et al. 2013

Chemistry A European J

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“…Although only 0.25 equiv. The vinyl group in a 1methyl-l-vinyl-substituted epoxide 8 does not affect the normal regioselectivity that gives the more-substituted alcohol. Both the reactivity and regioselectivity are highly dependent on the substitution pattern of the epoxides.…”

Section: Metal Hydridesmentioning

confidence: 98%

“…A dramatic reverse in selectivity was observed for 2-substituted cyclohexene oxide by simply changing the t-butyl group to a TMS or trimethylgermyl group,14 as depicted in equation (8 …”

Section: Cpmentioning

confidence: 99%

Reduction of Epoxides

Murai

Katō

1991

Comprehensive Organic Synthesis

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“…Although it has been reported (8,9) that the reaction products of 2-lithio-2-butene with various electrophiles retained the configuration of the starting material, we obtained only the Z-type of alcohol from both the Z-and E-2-lithio-2-butenes, but the mechanism was not clear in this reaction. On the other hand, the Eand Z-type of alcohols have previously been prepared by two groups (10,11). A convenient method using easily available starting materials has just been developed in our laboratory.…”

Section: 'Chimentioning

confidence: 99%

Studies on the Syntheses of Heterocyclic Compounds. Part DCXXXVI. An Alternative Synthesis of Pentazocine

Kametani¹,

Honda²,

Huang³

et al. 1975

Can. J. Chem.

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TETSUJI KAMETANI, TOSHIO HONDA, SHYH-PYNG HUANG, and KEIICHIRO FUKUMOTO. Can. J. Chern. 53, 3820-3823 (1975).The important starting material in a synthesis of pentazocine (1) was easily prepared by treating gaseous formaldehyde with 2-lithio-2-butene. Both E-and Z-2-bromo-2-butenes (2, 3) gave the same Z-type of alcohol (4) which was converted into pentazocine.TETSUJI KAMETANI, TOSHIO HONDA, SHYH-PYNG HUANG et KEIICHIRO FUKUMOTO. Can. J. Chern. 53,3820-3823 (1975).On a pr6par6, par rkaction de la formaldehyde i l'dtat gazeux avec le lithio-2 butkne-2, le compos6 important pour la synthke de la pentazocine (1). Les deux bromo-2 butiines-3 E et Z (2,3) conduisent au m2me alcooI de type Z (4) qui peut &re transform6 en pentzzocine. praduit par le journal]Previously, we reported two simple syntheses of pentazocine (1) (1, 2), an analgesic agent having no addiction liability (3-7), by PictetSpengler type reaction and Bischler-Napieralski type reaction. In both cases, the starting material is a mixture of two isomers, l-cyano-2-methyl-lbutene (14) and 1-cyano-2-methyl-2-butene (13), obtained by condensation of ethyl methyl ketone with cyanoacetic acid, and the stereochemistry of both compounds (13 and 14) is unknown. In order to clarify these points we have investigated the selective synthesis of 1-cyano-2-methyl-2-butene (6) whose stereochemistry was also determined easily, and here we wish to report a novel synthesis of 2-type 1-cyano-2-methyl-2-butene and the conversion of 6 into pentazocine (1).The lithium derivatives (8) of E-and 2-2-bromo-2-butenes were prepared at -10 to -20°C by reaction with lithium metal, and these were treated with formaldehyde gas separately to give the same 2-type alcohol (4) in 63% yield. The structure was easily determined by n.m.r. spectral analysis which showed a methylene proton at 6 3.96 as a singlet, indicating a 2-type olefin, while the corresponding signal in the E-isomer (1 1) should appear at higher field (6 3.75-3.80). It has been reported by Lenox and Katzenellenbogen (I 1) that both the E-and 2-isomer were separable by gas chroma- For personal use only.

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Stereoselective method for the synthesis of both olefinic isomers from a single precursor. Conjugate reduction of .alpha.,.beta.-unsaturated epoxides

Cited by 54 publications

References 0 publications

Collective Total Synthesis of Englerin A and B, Orientalol E and F, and Oxyphyllol: Application of the Organocatalytic [4+3] Cycloaddition Reaction

Collective Total Synthesis of Englerin A and B, Orientalol E and F, and Oxyphyllol: Application of the Organocatalytic [4+3] Cycloaddition Reaction

Reduction of Epoxides

Studies on the Syntheses of Heterocyclic Compounds. Part DCXXXVI. An Alternative Synthesis of Pentazocine

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