The stereochemistry of quassin

Valenta, Z.; Gray, A.H.; Orr, D. E.; Papadopoulos, S.; Podešva, C.

doi:10.1016/s0040-4020(01)99298-1

Cited by 49 publications

(14 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The first compound of this family to be discovered, quassin ( 1 , Chart 1), is a renowned insecticide . It was isolated from Quassia amara in 1937 and its structure elucidated in the 1960s . Quassin ( 1 ) contains two α‐methoxyenone chromophores and its absolute configuration was established in a seminal paper by Harada and colleagues by applying the electronic circular dichroism (ECD) exciton chirality method to the two preexisting enones.…”

Section: Introductionmentioning

confidence: 99%

Exciton coupling between enones: Quassinoids revisited

Bari

2017

Chirality

View full text Add to dashboard Cite

The electronic circular dichroism (ECD) spectra of two previously reported quassinoids containing a pair of enone chromophores are revisited to gain insight into the consistency and applicability of the exciton chirality method. Our study is based on time-dependent Density Functional Theory calculations, transition and orbital analysis, and numerical exciton coupling calculations. In quassin (1) the enone/enone exciton coupling is quasi-degenerate, yielding strong rotational strengths that account for the observed ECD spectrum in the enone π-π* region. In perforalactone C (2) the nondegenerate coupling produces weak rotational strengths, and the ECD spectrum is dominated by other mechanisms of optical activity. We remark the necessity of a careful application of the nondegenerate exciton coupling method in similar cases.

show abstract

Section: Introductionmentioning

confidence: 99%

Exciton coupling between enones: Quassinoids revisited

Bari

2017

Chirality

View full text Add to dashboard Cite

show abstract

“…Of the seven chiral centers present, those marked * in formula 1 are particularly crucial synthetically. The remaining three, marked 0 , can be established in later stages of the synthesis since neoquassin (2) has been found to deuterate at these positions in base without epimerization (1,2). We now wish to report a synthetic strategy which illustrates the use of a catalytic orientation reversal in Diels-Alder reactions (4), solves the stereochemistry at the four C*'s, and provides for the development of the desired oxygen functionality.…”

mentioning

confidence: 99%

A Synthetic Approach to Quassin. Introduction of Functionality and Stereochemistry by a Diels–Alder Reaction

Stojanac¹,

Sood²,

Stojanac³

et al. 1975

Can. J. Chem.

View full text Add to dashboard Cite

show abstract

“…The complete structure and relative stereochemistry of quassin, a bitter principle from Quassia atnara, has been established by Valenta et al (3,4). Early studies showed that bisnorquassin was not a simple bis-demethylated quassin, but in view of its ultraviolet (u.v.)…”

mentioning

confidence: 99%

Crystal and molecular structure of the m-bromobenzoate derivative of bisnorquassin

Lynton¹

1970

Can. J. Chem.

View full text Add to dashboard Cite

The molecular structure of the in-bromobenzoate derivative of bisnorquassin, C,,H2,0,Br, has been determined by the heavy atom method. The compound crystallizes in the orthorhombic system, space group P2,2,2,, with unit cell dimensions n = 20.09 + 0.02 A, b = 14.63 f 0.02 A, c = 8.06 + 0.01 A and 4 molecules in the unit cell. Final atomic parameters have been obtained from a blockdiagonal least-squares refinement using anisotropic temperature parameters. The final agreement residual for I665 observed reflections is R = 0.107.The structure of bisnorquassin previously proposed by Findlay and Cropp, on the basis of spectroscopic and chemical evidence, is shown to be essentially correct.Canadian Journal of Chemistry, 48, 307 (1970) Introduction Bisnorquassin, C2,H2,0,, was first prepared by Robertson et al. (1,2) by the treatment of both quassin and norquassin with a warm mixture of concentrated hvdrochloric and acetic acids. The complete structure and relative stereochemistry of quassin, a bitter principle from Quassia atnara, has been established by Valenta et al. (3,4). Early studies showed that bisnorquassin was not a simple bis-demethylated quassin, but in view of its ultraviolet (u.v.) absorption spectrum, possessed an extended system of conjugation.A structure for bisnorquassin has been given by Findlay and Cropp (5) which is adequately supported by spectroscopic and chemical evidence. This structure is not comwlete in that the stereochemical co~lfiguration about certain carbon centers is not established. This X-ray analysis was undertaken to provide the complete stereochen~ical structure of this interesting compound.

show abstract

The stereochemistry of quassin

Cited by 49 publications

References 6 publications

Exciton coupling between enones: Quassinoids revisited

Exciton coupling between enones: Quassinoids revisited

A Synthetic Approach to Quassin. Introduction of Functionality and Stereochemistry by a Diels–Alder Reaction

Crystal and molecular structure of the m-bromobenzoate derivative of bisnorquassin

Contact Info

Product

Resources

About