- Hydrolysis of 1,4,6-trioxaspiro[4.5]decanes to δ-lactones using 2,3- dichloro-5,6-dicyanobenzoquinone in aqueous acetone
-
A selective hydrolysis of 1,4,6-trioxaspiro[4.5]decane orthoesters by 2,3- dichloro-5,6-dicyanoquinone (DDQ) in aqueous acetone in the presence of other acid-sensitive ketals is suggested to involve the formation of a charge- transfer complex followed by hydrolysis. A hydride-transfer mechanism for this oxidation was excluded.
- Vasudevan,Watt
-
-
Read Online
- A Concise Enantioselective Approach to Quassinoids
-
A synthetic approach to quassinoids is described. The route to the tetracyclic core relies on an efficient and selective annulation between two unsaturated carbonyl components that is initiated by catalytic hydrogen atom transfer from an iron hydride to an alkene. Application of this strategy allows for enantioselective synthesis of quassin, which is prepared in 14 steps from commercially available starting material.
- Thomas, William P.,Pronin, Sergey V.
-
p. 118 - 122
(2022/01/08)
-
- Total Synthesis of (+)-Quassin
-
A total synthesis of (+)-quassin from naturally occurring (S)-(+)-carvone is described. The total number of steps was 28, and the overall yield was about 2.6%. The synthetic strategy for the construction of the tetracyclic carbon framework was based on a C→ABC→ABCD ring annulation sequence, involving an aldol reaction, an intramolecular Diels - Alder reaction, and an intramolecular acylation as the key steps. Subsequent functionalization of ring A and ring C then afforded the target (+)-quassin.
- Shing, Tony K. M.,Jiang, Qin
-
p. 7059 - 7069
(2007/10/03)
-
- Total synthesis of d,l-quassin
-
The completion of the total synthesis of d,l-quassin 1 is described.Key steps are a facile intramolecular acylation of a protected cyanohydrin carbanion (4 -> 5), a selective deprotonation with trioctyl methyl ammonium hydroxide leading to the removal of HCN from 8, and the unusual sequence 5 -> 12 in which the ring C enol ether of 5 is converted selectively into ring C diosphenol of 12. Key words: quassin, synthesis, selective base, diophenols, acylation.
- Stojanac, Nada,Valenta, Zdenek
-
p. 853 - 855
(2007/10/02)
-
- ON EQUILIBRATION OF QUASSIN AND 4-EPIQUASSIN
-
Equilibration of quassin and 4-epiquassin is described.Various quassin derivatives are characterized and their relationship to quassin (I) is discussed.A regioselective deprotonation is achieved in quassin and 4-epiquassin (III) by the introduction of a diosphenolate grouping which makes a potentially acidic H-atom unavailable for attack by base.
- Stojanac, Nada,Valenta, Zdenek
-
p. 2298 - 2305
(2007/10/02)
-
- A PARTIAL SYNTHESIS OF PICRASIN B AND Δ2-PICRASIN B1
-
The regioselective reductive demethylation of the O-methyldiosphenol functionality in the A ring of quassin (3) with chlorotrimethylsilane and sodium iodide furnished picrasin B (1).Swern oxidation of 1 furnished Δ2-picrasin B (2), and O-methylation of 2 regenerated quassin (3).
- Kenji, Kawada,Moonsun, Kim,Watt, David S.
-
p. 5985 - 5988
(2007/10/02)
-
- A NEW NEOQUCASSIN DERIVATIVE FROM QUASSIA AMARA
-
A new cassinoid, a dihydroneoquassin, has been isolated from Quassia amara wood.In addition the known compounds, paraine and isoparaine, were also identified.Moreover, the known 4-methoxy-5-hydroxycantin-6-one was isolated for the first time from the same source.The structure and stereochemistry of 11-dihydro-12-nor-neoquassin were determined by spectroscopic methods as well as by means of chemical correlations.Key Word Index - Quassia amara; Simarubaceae; quassinoids; dihydronorneoquassin.
- Grandolini, G.,Casinovi, C. G.,Barbetti, P.,Fardella, G.
-
p. 3085 - 3087
(2007/10/02)
-
- QUASSINOIDS: TOTAL SYNTHESIS OF DL-QUASSIN
-
The total synthesis of quassin (1), the major constituent of quassia wood, is described in racemic form.The synthesis features the Lewis acid catalyzed intermolecular Diels-Alder reaction between dienophile 8 and ethyl (E)-4-methyl-3,5-hexadienoate (9).Di
- Vidari, Giovanni,Ferrino, Sergio,Grieco, Paul A.
-
p. 3539 - 3548
(2007/10/02)
-
- SYNTHETIC STUDIES ON QUASSINOIDS: A STEREOSELECTIVE CONSTRUCTION OF THE PICRASANE SKELETON
-
12β-Hydroxypicrasan-3-one, a compound having the correct relative stereochemistry of all the six ring-juncture chiral centers of the picrasane skeleton, was synthesized from a known tricyclic compound, using the orthoester Claisen rearrangement and lead tetraacetate oxidation as key reactions.
- Miyaji, Katsuaki,Nakamura, Toshio,Hirota,, Hiroshi,Igarashi, Michito,Takahashi, Takeyoshi
-
p. 5299 - 5302
(2007/10/02)
-
- PICRANOSIDE-A, A NOVEL QUASSINOID GLUCOSIDE FROM PICRASMA AILANTHOIDES PLANCHON
-
A novel quassinoid glucoside picrasinoside-A was isolated from Picrasma ailanthoides PLANCHON and the structure was established from spectral data, chemical transformations into picrasin B and quassin, and enzyme hydrolysis.The aglycon picrasin B showed a significant clastogenic activity in cell cultures of Don lung cells of Chinese hamster.
- Okano, Masayoshi,Fukamiya, Narihiko,Kondo, Katsuhiko,Fujita, Tomoyuki,Aratani, Takaaki
-
p. 1425 - 1426
(2007/10/02)
-
- QUASSINOIDS. ISOLATION FROM SOULAMEA MUELLERI AND STRUCTURES OF 1,12-DI-O-ACETYL SOULAMEANONE AND Δ2-PICRASIN B. X-RAY ANALYSIS OF SOULAMEANONE
-
The structures of soulameanone, 1,12-di-O-acetyl soulameanone and Δ2-Picrasin B, new quassinoids from Soulamea muelleri (Simaroubaceae), were determined by spectrometric methods and chemical correlation, and that of Soulameanone confirmed by single crystal X-ray analysis.
- Polonsky, Judith,Tri, Mai Van,Varon, Zoia,Prange, Thierry,Pascard, Claudine,et al.
-
p. 2983 - 2988
(2007/10/02)
-