Synthesis and biological inactivity of some 4.alpha.,6-cyclo steroids

Ft, Bond; Weyler, Walter; Brunner, Bernhard; Je, Stemke

doi:10.1021/jm00224a011

Cited by 4 publications

(2 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Unfortunately, overlap of the H-18 and H-2a resonances prevented a similar measurement in 17~-tert-butyldimethylsiloxy-19(S)-chloro-5a, 19a-cycloandrostan-3-one (11). The values for 3J( la,2a) and 3J (18,28) are suggestive of a ( 2 -1 4 -2 torsion angle of ca 50". 2J(2a,2p) indicates C -2 4 -3 torsion angle of less than 20", while 2J(4a,4p) indicates a C-3-C-4 torsion angle of ca 50".…”

Section: Inmentioning

confidence: 98%

“…This observation, and the relative sizes of 3J( la,2/3) and 3J(lfl,2a), suggest that in 9 the conformer with H-la and H-4a axial is predominant. Spectral overlap prevented NOE measurements from the C-4 protons in 14 and 15, however, the relative sizes of 3J(la,28) and 3J( 18,201) suggest that the two possible conformations must have comparable energies.The only stereospecific coupling in 5p,19cycloandrost-l-ene-3,17-dione (16) is 2J(4a,4/3), and the relatively high value indicates a very low C-3-C-4 torsion angle, consistent with the expected near planarity of ring A. 5a,l9a-Cycloandrostanes (10-12)…”

mentioning

confidence: 99%

See 1 more Smart Citation

Ring a conformation in steroids. 3—Cyclosteroids and cyclopropanosteroids

Marat

Templeton

Ling

et al. 1995

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

Proton and carbon NMR data are provided for 21 ring A and ring B cyclosteroids and cyclopropano (or methylene) steroids. Shift assignments were made using standard 2D NMR techniques, whie ring A proton subspectra were extracted with a 1D TOCSY experiment. Coupling constants were obtained from iterative spin system simulation of these sub-spectra. Ring A conformations were determined from the two-and three-bond protoeproton couplings and NOE measurements. The utility and limitations of extended Karplus-type equatioas, the effect of cyclopropyl groups on vicinal and geminal couplings and cyclopropane-induced chemical shifts are discUSSed.

show abstract

Section: Inmentioning

confidence: 98%

mentioning

confidence: 99%

Ring a conformation in steroids. 3—Cyclosteroids and cyclopropanosteroids

Marat

Templeton

Ling

et al. 1995

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

show abstract

Intramolecular Reactions of Diazocarbonyl Compounds

Burke

Grieco

1979

Organic Reactions

View full text Add to dashboard Cite

Since the demonstration by Stork and Ficini in 1961 that unsaturated diazoketones undergo intramolecular cyclization to form cyclopropanes the intramolecular reactions of α‐diazocarbonyl compounds have been extensively studied under thermal, catalytic, and photochemical conditions. Intramolecular cyclization of α‐carbonyl carbenes and carbenoids has found widespread application to the synthesis of theoretically interesting compounds such as bullvalene, twistane, bridged annulenes, and barbaralone, as well as syntheses of natural products such as sabinene, sirenin, α‐chamigrene, and phyllocladene. The reaction has also allowed the construction of several intriguing polycyclic systems that were unattainable by alternative methods. A recent review has covered the reactions of diazoacetic esters with alkenes, alkynes, heterocyclics, and aromatic compounds. Unsaturated alkoxycarbonyl carbenes (:CHCO 2 R) and unsaturated carbonyl carbenes (:CHCOR) (where R contains either aromatic or olefinic groups), which are considered to be intermediates in the absence of catalyst, have been the subject of several other reviews. A review concerning photochemically, thermally, and catalytically induced Wolff rearrangements of α‐diazocarbonyl compounds has recently appeared. However to date no comprehensive review has appeared which demonstrates the synthetic potential of α‐diazocarbonyl insertion and addition reactions. In reviewing the reactions of α‐diazocarbonyl compounds chosen not to include certain peripheral topics such as intermolecular reactions, intramolecular dimerization of bis(α‐carbonyl carbenoids) to give diacyl cycloolefins and intramolecular trimerizations of tris(α‐keto carbenoids), affording triacylcyclopropanes are not included. Also excluded are base‐catalyzed reactions of α‐diazocarbonyl compounds and certain ring‐contraction reactions involving CC bond insertion of intermediate α‐ketocarbenes. The topics included in this report are the intramolecular reactions of α‐carbonyl carbenes and carbenoids with olefinic and aromatic unsaturation, with CH bonds, and with CC and NH single bonds. Also included are acid‐catalyzed cyclization reactions of α‐diazoketones.

show abstract