Hydroboration of terpenes.  VI.  Hydroboration of .alpha.- and .beta.- cedrenes.  Configurational assignments for the related cedrane derivatives

Acharya, Shrinivas P.; Brown, Herbert C.

doi:10.1021/jo00826a042

Cited by 37 publications

(36 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…8.) In-this series (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15), as expected, the chemical shifts of the quaternary C-1, tertiary C-2 and C-7, secondary C-3 and C-4 and methyls-12 and -14 are not much influenced by the differents functionalities. This is fairly reasonable if one considers, on the one hand, the rigidity of the cis fused bicyclo [3.3.0]octane part of the molecular framework and, on the other, the relative positions of the polar group (always on C-9) and of the various substituents.…”

Section: Resultssupporting

confidence: 70%

Structural studies in the cedrane series by ¹³C NMR

Brun

Casanova

Raju

et al. 1987

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

The complete analysis of the "C NMR spectra of 30 cedrane derivatives with various functionalities on the 2,6, 6,8-tetramethyltricycl0[5.3.1*~~0~~~]undecane skeleton is reported. The assignment of the signals to the appropriate carbons bas been made using the various functionalities on the molecular framework and the chemical shift theory (a, f3, y effects). When necessary, off-resonance decoupling, I N E R and DEPT experiments have been used, as well as specific deuterium labelling. The last ambiguities were resolved with the aid of lanthanide shift reagents and SFORD experiments. The assignments for the reference compounds neoisocedranol oxide, cedrol and cedrene were made using the carbon-carbon connectivity 2D INADEQUATE pulse sequence. The examination of cedrane derivatives functionalized on C-9 (carbonyl, hydroxyl, acetate) and C-8 (methyl, axial or equatorial) showed that the "C chemical shifts of C-5, -6, -11 and -13 are sensitive probesfor the conformation of the six-membered ring (ring C), which is essentially a flattened chair, and for the stereochemistry of the C-8 and C-9 substituents. Comparison with 2-methylbicyclo[3.2.l]octan-3-ones shows that the Anti Reflex effect is operative in cedrane derivatives.Cedrane oxides and their derivatives have also been examined and the corresponding "C data are reported. Using all this inforniation it was possible to carry out a complete analysis of lac acids, which have a functionalized tricycl0[5.3~", O1.sJundecane framework like the cedrane derivatives. The "C spectral analysis shows that, from the structural point of view, this tricyclic system behaves as a bicyclo[3.3.0] skeleton with an additional three-carbon bridge between C-1 and C-7, rather than as a bicyclo[3.2.l]octane with an additional cyclopentane fused on C-1 and C-5; when additional strain is introduced into this system, the five-membered ring A and the six-membered ring C undergo conformational deformations more easily than ring B.

show abstract

Section: Resultssupporting

confidence: 70%

Structural studies in the cedrane series by ¹³C NMR

Brun

Casanova

Raju

et al. 1987

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

show abstract

“…Cedranol acetates 1-4 are tricyclic sesquiterpene derivatives which belong to a naturally occurring family with the (3R,3aR,7S,8aS)-3,6,8,8-tetramethyl-3a,7-methanoperhydroazulene skeleton, whose relative stereochemistry at C5 and C6 has been established by 1 H and 13 C NMR. 37,40 Diastereomers 1-4 have molecular formula C 17 H 28 O 2 , with 19 heavy atoms, 146 electrons, and 135 vibrational frequency modes that are active vibrations in the IR and VCD spectra. In the 1550-950 cm -1 region, 61 out of these 135 vibrational modes are present for each diastereomer.…”

Section: Resultsmentioning

confidence: 99%

Vibrational Circular Dichroism Discrimination of Diastereomeric Cedranol Acetates

Gordillo-Román¹,

Camacho-Ruiz²,

Bucio³

et al. 2013

Chirality

View full text Add to dashboard Cite

The reliability of vibrational circular dichroism (VCD) spectroscopy to discriminate four diastereomeric cedranol acetates 1-4 by means of their absolute configuration is examined. The usage of CompareVOA software to quantify comparisons of the measured infrared (IR) and VCD spectra with the corresponding simulated spectra at the B3LYP/DGDZVP and B3PW91/DGDZVP levels of theory for each diastereomer enabled the B3PW91 functional to be qualified as superior to the B3LYP functional for vibrational calculations of 1-4. Analogously, a set of quantitative VCD spectra cross-comparisons of 1-4 unambiguously distinguished the diastereomers using B3PW91 and failed using B3LYP. Remarkably, quantitative IR spectra cross-comparisons of 1-4 using B3PW91 or B3LYP functionals demonstrated that the achiral spectroscopic IR technique is not able to distinguish cedranol acetate diastereomers. VCD comparisons using anisotropy g-factor values of bands in the 1550-950 cm(-1) region of the spectra were of aid to facilitate visual spectra matching for each diastereomer.

show abstract

“…Reaction of labeled ot-cedrene-12-t/ (9) with w-chloroperbenzoic acid (12) gave exo-5,6-epoxycedrane-12-d (10) (12). Its reduction with LiAlH4 afforded 6-isocedrol-12-¿/ (lib) as shown by 'H-nmr analysis.…”

mentioning

confidence: 89%