Boat Forms of Ring A in B-Norsteroids

Hanson, James R.; Hitchcock, Peter B.; Kıran, İsmail; Uyanık, Cavit

doi:10.1039/a903512e

Cited by 7 publications

(9 citation statements)

References 10 publications

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“…Thus, when the 5,6-epoxysteroid is converted into 5-methyl-Á 9(10) -19-norsteroid (I), a strong relief in the twist of steroid nucleus is observed. On the other hand, low values for the C19-C10Á Á ÁC13-C18 pseudotorsion angle are found in the literature for several 5,6epoxysteroids (Hanson, Hitchcock & Nagaratnam, 1999;Hanson, Hitchcock & Kiran, 1999;Litvinovskaya et al, 1995).…”

Section: Commentmentioning

confidence: 82%

6β-Hydroxy-5β-methyl-20-oxo-19-norpregn-9(10)-en-3β-yl acetate

et al. 2009

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In the title compound, C(23)H(34)O(4), which is an intermediate in the synthesis of pregnane derivatives with a modified skeleton that show potent abortion-inducing activity, the conformation of ring B is close to half-chair due to the presence of both the C=C double bond and the axial 5beta-methyl group. Rings A and C have conformations close to chair, while ring D has a twisted conformation around the bridgehead C-C bond. Molecules are hydrogen bonded via the hydroxyl and acetoxy groups into infinite chains. Quantum-mechanical ab initio Roothan Hartree-Fock calculations show that crystal packing might be responsible for the low values of the angles between rings A and B, and between ring A and rings C and D, as well as for a different steric position of the methyl ketone side chain compared to the geometry of the free molecule.

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Section: Commentmentioning

confidence: 82%

6β-Hydroxy-5β-methyl-20-oxo-19-norpregn-9(10)-en-3β-yl acetate

et al. 2009

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“…34 Other 5β-B-norandrostane-3-ketones also possess ring A in twisted boat forms. 35 A possible explanation of the existence of ring A in the boat forms is that these conformations reduce the interaction between C-1 and C-11 and between the C-4 and C-6 substituents.…”

Section: Stability Of the Ring Junctionsmentioning

confidence: 99%

The Chemistry of B-Norsteroidal 6-Ketones and their Relatives

Uyanık

Hanson

2011

Journal of Chemical Research

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His research interests include thechemistry and biosynthesis of natural products particularly terpenoids, steroids and fungal metabolites. Over the past 50 years he has published over 500 papers and reviews and 12 books. Introduction 2 Synthesis 3 Stability of the ring junctions 4 Bromination of the 6-ketones 5 Reduction of the ketones 6 Grignard reactions of 6-ketones 7 Beckmann rearrangement of 6-oximino-Bnorsteroids 8 Conclusion 9 References

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“…In the B-nor series, the nature of the ring junction can affect the geometry of ring A. 8 The X-ray crystal structures of B-nor-5b-androstanes-3,6-dione 2, 6b-methoxycarbonyl-3b,5b -dihydroxy-B-norandrostan-17-one 3 and 6b-toluenep-sulfonyloxymethyl-5b-hydroxy-B-norandrostan-3,17-dione 4 reveal that ring A exists in a boat or twisted boat form in these B-nor-5b-androstanes. On the other hand, ring A existed in a more normal chair form in 3b, 6b-dihydroxy-B-nor-5a-androstane 5.…”

Section: Addition Of Brominementioning

confidence: 99%