A new circular dichroism study of ketal formation of some steroidal ketones

Zalkow, Leon H.; Hale, R.; French, Kristen L.; Crabbé, Pierre

doi:10.1016/s0040-4020(01)93146-1

Cited by 12 publications

(2 citation statements)

References 17 publications

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“…The configuration of the 17-OH group was proved to be a, because the hydrolysis products 5a and 5b and the acetyl derivative 6 obtained from 5a were different in all respects from their epimers prepared previously1 from optically active Torgov's secolone (with 17/3-OH). Subsequently, compound 6 was converted by standard methods into rac-3-methoxy-14/3-hydroxy-8a-estra-l,3,5(10)-trien-17-one (9). The latter compound had a MS spectrum identical with that reported by Wulfson et al4 Direct comparison of our sample 9 with the compound prepared by Zakharychev et al5 confirmed their identity.…”

Section: T H Isupporting

confidence: 78%

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Chiroptical properties of pelletierine and anaferine

Craig¹,

Lee²,

Roy³

1978

J. Org. Chem.

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Section: T H Isupporting

confidence: 78%

“…Subsequently, compound 6 was converted by standard methods into rac-3-methoxy-14/3-hydroxy-8a-estra-l,3,5(10)-trien-17-one (9). The latter compound had a MS spectrum identical with that reported by Wulfson et al4 Direct comparison of our sample 9 with the compound prepared by Zakharychev et al5 confirmed their identity.…”

Section: T H Isupporting

confidence: 78%

Chiroptical properties of pelletierine and anaferine

Craig¹,

Lee²,

Roy³

1978

J. Org. Chem.

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ChemInform Abstract: NEUARTIGE UNTERSUCHUNGSMETHODE DER KETALBILDUNG BEI EINIGEN STEROIDKETONEN DURCH CIRCULARDICHROISMUS

Zalkow¹,

Hale²,

French³

et al. 1971

Chemischer Informationsdienst. Organische Chemie

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Dimethyl ketals of methylcyclohexanones as fragmentation‐directing derivatives

Manni

Cooper

Hardesty

1972

Org. Mass Spectrom.

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Abstract-The mass spectra of dimethyl ketal derivatives of cyclohexanone and the 2-, 3-and 4-methylcyclohexanones are discussed relative to their usefulness in indicating the point of alkyl substitution. Major fragments in the spectra (m/e 101 and m/e 115) arise by cr-cleavage, hydrogen rearrangement and further cleavage to give even-electron species. The spectra yield structural information equivalent to that obtained from the corresponding ethylene ketals. The ease of preparation of dimethyl ketals and the mildness of reaction conditions relative to ethylene ketals warrant further exploitation of dimethyl ketals as fragmentation-directing derivatives in mass spectrometry. I N T R O D U C T I O NTHE ABILITY to predict fragments that will arise from electron-impact induced cleavage of organic molecules is enhanced greatly when moieties are present that will force fragmentation to occur in a specific manner. Outstanding among these fragmentationdirecting derivatives are the ethylene acetals and ethylene keta1s.l Scant attention appears to have been paid to the mass spectra of dimethyl ketals of cyclic ketones. This may be due in part to a report2 indicating that in the mass spectrum of 3,3-dimethoxyandrostane peaks arising by a-cleavage are of only moderate intensity compared with [M -31]+, whereas it is known that fragmentation by a-cleavage predominates in the spectra of ethylene ketals. Another factor may be evidence of decomposition of ketals to alkenyl ethers in the ion source of a mass ~pectrometer.~?~ Our interest in the mass spectra of acetals and the alkenyl ethers derived from them5 led us to measure the spectra of dimethyl ketals of methylcyclohexanones. Examination of these spectra indicated that dimethyl ketals would be valuable fragmentation-directing derivatives for cyclohexanones especially in applications involving combined gas chromatography-mass spectrometry (g.c.-m.s.). RESULTS A N D DISCUSSIONThe mass spectral fragmentation of the dimethyl ketals of cyclohexanone (I), 2-methylcyclohexanone (II), 3-methylcyclohexanone (111) and 4methylcyclohexanone (IV) are summarized in Scheme 1. Mechanistically, the cleavages are analogous to those described for a number of substituted cyclohexanes.6 From the standpoint of structure determination the most significant peaks are produced by a-cleavage followed by hydrogen migration with subsequent scission (3 $ 3 4, 4 5 5 5) to produce even-electron species (m/e 101, m/e 115).In all cases a pronounced [M -31]+ peak is seen. Unlike the case of 3,3-dimethoxyandrostane,2 however, a-cleavage predominates and the base peak in the spectra of I to I V is either m/e 101 or m/e 115. The difference in intensity between

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A new circular dichroism study of ketal formation of some steroidal ketones

Cited by 12 publications

References 17 publications

Chiroptical properties of pelletierine and anaferine

Chiroptical properties of pelletierine and anaferine

ChemInform Abstract: NEUARTIGE UNTERSUCHUNGSMETHODE DER KETALBILDUNG BEI EINIGEN STEROIDKETONEN DURCH CIRCULARDICHROISMUS

Dimethyl ketals of methylcyclohexanones as fragmentation‐directing derivatives

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