<b>The Conformations of Substituted Cyclopentanes. III. Ring D in the Steroids</b>

Brutcher, Frederick V.; Bauer, William R.

doi:10.1021/ja00870a042

Cited by 54 publications

(14 citation statements)

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“…The torsion angles of C(6)-C(7) and C(6)-C(1 I) of -16"1 and 13-6 ° show that the highest strain occurs in these two bonds. The torsion angles of the five-membered rings B and C are within 5 ° of the values for the maximally puckered envelope model for fused ring systems of Brutcher & Bauer (1962). C(4) is equidistant from the mean planes of the other four atoms of each of these two rings, but the four atoms of ring B are less planar than those of ring C (Table 4).…”

Section: Conformational Analysissupporting

confidence: 60%

The crystal and molecular structure of a tetracyclic bromobenzoate, C21H23O2Br

Przybylska¹,

Ahmed²

1974

Acta Crystallogr Sect B

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The title compound, C21Hz302Br, is part of the skeleton of the aconite alkaloids. The crystals are in space group P21/e with a = 6.312 (3), b = 15.577 (3), c = 18.267 (5) A, fl= 90.99 (3) °, Z= 4. The structure was determined by the heavy-atom method, and refined by block-diagonal least-squares calculations to R= 0.046 for the 2545 observed reflexions. The strain caused by the fusion of rings in the molecule results in considerable variations in the C-C single-bond lengths to values between 1-500 and 1-587 (5) A, the longest being that shared by the six-and four-membered rings.

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Section: Conformational Analysissupporting

confidence: 60%

The crystal and molecular structure of a tetracyclic bromobenzoate, C21H23O2Br

Przybylska¹,

Ahmed²

1974

Acta Crystallogr Sect B

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“…The torsion angles of the five-membered rings, B and C, are within 6 ° of the half-chair model for fused-ring systems (Brutcher & Bauer, 1962). The torsion angles of the norbornane system indicate the presence of synchro-twist (Altona & Sundaralingam, 1970).…”

Section: Meo~ Meo H R Mementioning

confidence: 59%

Chasmanine intermediate, C₂₄H₃₅NO₆

Przybylska¹,

Ahmed²

1980

Acta Crystallogr Sect B

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“…In dieser Form liegen vier Atome, namlich C-14, C-15, C-16 und C-17, in einer Ebene, wahrend C-13 sich ausserhalb der Ebene befindet (Tabelle 2h). Dieser Befund ist in ubereinstimmung mit Berechnungen von BRUTCHER & BAUER [5], welche zeigen, dass fur trans-Verknupfung von Ring C und D und 17/?-Substituent dieses ((C-13-Envelope)) energetisch etwas giinstiger sein sollte als die Halbsessel-oder die entsprechende aC-14-Envelope))-Form. Die berechnete Energiedifferenz zwischen der Halbsessel-' ) und der ((C-13-Envelopeo-Konformation ist jedoch sehr klein (0,5 kcal/Mol), und es ist daher nicht uberraschend, wenn ROMERS et al [6] im 4-Brom-9,!I,lOa-pregna-4,6-dien-3,20dion Ring D als Halbsessel vorfinden.…”

Section: -En-3-onunclassified