70238-41-4Relevant academic research and scientific papers
Ring-closing metathesis approaches towards the total synthesis of rhizoxins
Altmann, Karl-Heinz,Liniger, Marc,Neuhaus, Christian M.
supporting information, (2020/10/18)
Efforts are described towards the total synthesis of the bacterial macrolide rhizoxin F, which is a potent tubulin assembly and cancer cell growth inhibitor. A significant amount of work was expanded on the construction of the rhizoxin core macrocycle by ring-closing olefin metathesis (RCM) between C(9) and C(10), either directly or by using relay substrates, but in no case was ringclosure achieved. Macrocycle formation was possible by ring-closing alkyne metathesis (RCAM) at the C(9)/C(10) site. The requisite diyne was obtained from advanced intermediates that had been prepared as part of the synthesis of the RCM substrates. While the direct conversion of the triple bond formed in the ring-closing step into the C(9)-C(10) E double bond of the rhizoxin macrocycle proved to be elusive, the corresponding Z isomer was accessible with high selectivity by reductive decomplexation of the biscobalt hexacarbonyl complex of the triple bond with ethylpiperidinium hypophosphite. Radical-induced double bond isomerization, full elaboration of the C(15) side chain, and directed epoxidation of the C(11)-C(12) double bond completed the total synthesis of rhizoxin F.
Diastereomerically and enantiomerically pure 2,3-disubstituted pyrrolidines from 2,3-aziridin-1-ols using a sulfoxonium ylide: A one-carbon homologative relay ring expansion
Schomaker, Jennifer M.,Bhattacharjee, Somnath,Yan, Jun,Borhan, Babak
, p. 1996 - 2003 (2007/10/03)
An ylide-based aza-Payne rearrangement of 2,3-aziridin-1-ols leads to an efficient process for the preparation of pyrrolidines. The aza-Payne rearrangement under basic reaction conditions favors the formation of epoxy amines. Subsequent nucleophilic attack of the epoxide by the ylide yields a bis-anion, which upon a 5-exo-tet ring-closure yields the desired pyrrolidine, thus completing the relay of the three-membered to the five-membered nitrogen-containing ring system. This process takes place with complete transfer of stereochemical fidelity and can be applied to sterically hindered aziridinols.
Convenient synthesis of labdane and drimane analogues with o-quinol functionality
Meenakshi,Sivaramkrishnan,Padmakumar,Hadimani, Shreeshailkumar B.,Bhat, Sujata V.
, p. 4065 - 4076 (2007/10/03)
The Diels-Alder reactions of 4-carbomethoxy-o-benzoquinone with substituted-1,3-dienes give high yields of the drimane and labdane analogues containing an orthoquinol moiety.
Synthesis of diastereomerically and enantiomerically pure 2,3-disubstituted tetrahydrofurans using a sulfoxonium ylide
Schomaker, Jennifer M.,Pulgam, Veera Reddy,Borhan, Babak
, p. 13600 - 13601 (2007/10/03)
Nucleophilic substitution reactions of 2,3-epoxy alcohols, easily prepared via Sharpless asymmetric epoxidation chemistry, offer access to a wide variety of enantiomerically pure compounds. In this communication, we describe the use of a Payne rearrangement to control regioselectivity in the ring-opening of a series of 2,3-epoxy alcohols with dimethylsulfoxonium methylide to yield diastereomerically and/or enantiomerically pure disubstituted tetrahydrofuran rings. The factors influencing the success and substitution pattern of the THF ring products are discussed, including steric, electronic, and solvent effects. Copyright
Acyclic Stereoselection in the Ortho Ester Claisen Rearrangement
Daub, G. William,Edwards, James P.,Okada, Carol R.,Allen, Jana Westran,Maxey, Claudia Tata,Wells, Matthew S.,Goldstein, Alexandra S.,Dibley, Michael J.,Wang, Clarence J.,Ostercamp, Daniel P.,Chung, Steven,Cunningham, Paula Shanklin,Berliner, Martin A.
, p. 1976 - 1985 (2007/10/03)
The ortho ester Claisen rearrangement of trisubstituted allylic alcohols exhibits significant levels of diastereoselection. In E allylic alcohols, a 1,3-diaxial interaction develops in the chairlike transition state leading to the anti isomer, rendering the reaction syn selective by a factor of 3-5 to 1. In Z allylic alcohols, the 1,3-diaxial interaction develops in the transition state leading to the syn isomer, generating an anti:syn selectivity of 6-15 to 1. The relative stereochemistry of the syn isomer was confirmed independently by the synthesis of the mycotoxin botryodiplodin.
Synthetic studies toward potent cytotoxic agent amphidinolide B : Synthesis of the entire C14-C26 moiety of the top half
Chakraborty, Tushar K.,Thippeswamy, Devasamudram,Suresh, Vayalakkada R.,Jayaprakash, Sarva
, p. 563 - 564 (2007/10/03)
Regioselective hydroboration of a 4-methyl-2-alkene, oxidation of the resulting mixture of isomeric alcohols, and finally diastereoselective reduction of the ketone are the key steps in the stereoselective synthesis of C19-C26 fragment of amphidinolide B
Stereoselective synthesis of a nonracemic hydronaphthalene subunit of Kijanolide
Marshall,Salovich,Shearer
, p. 2398 - 2403 (2007/10/02)
Lewis acid catalyzed Diels - Alder cyclization of the tetraenal 15 affords the endo product, hydronaphthalene 16, with high diastereoselectivity. Nonracemic 15 is prepared by addition of dienyne 5 to resolved (2S,4S)-5-[(tert -butyldimethylsilyl)oxy]-2,4-
Biohydrogenation of Unsaturated Compounds by Saccharomyces cerevisiae. Part 1. Stereochemical Aspects of the Reaction and Preparation of Useful Bifunctional Chiral Synthons
Ferraboschi, Patrizia,Grisenti, Paride,Casati, Rosangela,Fiecchi, Alberto,Santaniello, Enzo
, p. 1743 - 1748 (2007/10/02)
Ethyl 4,4-dimethoxy-3-methylbut-2-enoate (1; R=CO2Et) has been prepared as a mixture of (E)- and (Z)-isomers, the (E)/(Z) ratio depending on the base used.Each isomeric mixture of (1a) and (1b) has been used as substrate for biohydrogenation with fermenting Saccharomyces cerevisiae (baker's yeast) and the (Z)-isomer seems to be the preferred substrate. (E)-Unsaturated alcohols such as (3a) and (5d) are not reduced to the corresponding saturated hydroxy derivatives by baker's yeast.The (E)-aldehyde (3c) and its acetal (3d) are mainly reduced to the corresponding (E)-alcohol (3a), the saturated hydroxy ester (2a) being formed to a minor extent, especially with (3d).In contrast, biohydrogenation is also successful with the (E)-isomers of compounds (3e), (3f), and (3b) (R2=alkyl or alkenyl).If the allylic oxygenated group to be reduced is not α-methyl substituted, reduction to the corresponding saturated alcohols readily occurs with the (E)-isomers as in the case of (5f).For this last biohydrogenation, the stereochemistry of the methyl-bearing carbon has been established by chemical correlations.The α,β-disubstituted allylic acetal (6a) is not biohydrogenated by the yeast, but a mixture of unsaturated hydroxy ester (6b) and γ-hydroxy lactone (8) is recovered from the incubation.
A Stereoselective Synthesis of the Hydronaphthalene Substructure of Kijanolide
Marshall, James A.,Grote, Jonathan,Shearer, Barry
, p. 1633 - 1635 (2007/10/02)
The synthesis of a hydronaphthalene substructure of the antitumor antibiotic kijanimicin is described in which four of the seven chiral centers are introduced via a diastereoselective intramolecular Diels-Alder cyclization of an all-(E)-2,8,10,12-tetradec
Regio- and Stereo-selective Oxidation of gem-Dimethyl Olefins via -Sigmatropic Rearrangement of Allyl Amine Oxides
Inoue, Seiichi,Iwase, Norimichi,Miyamoto, Osamu,Sato, Kikumasa
, p. 2035 - 2038 (2007/10/02)
Highly regio- and stereo-selective oxidation sequences are described for the efficient conversion of the gem-dimethyl olefin terminus of acyclic terpenes to terminal trans-allylic alcohols and trans α,β-unsaturated aldehydes.
