On the elimination of methanol from stereoisomeric arylcyclohexyl methyl ethers under electron impact

Collision-induced dissociation study of stereospecific elimination processes of stereoisomeric phenylcyclohexanols and their derivatives upon electron ionization

“…7,8 This Ðnding is consistent with the large distance between that H-atom and the oxygen in the cis-isomers, which does not allow a 1,4-elimination involving the bezylic position. The major origin of the hydrogen atom abstracted in the course of this elimination has not been established in that study.…”

The mass spectrometric behavior of 3α,5-cyclo-5α-cholestan-6β-yl alkyl ethers

“…A number of studies of substituted cyclohexanols have established that electron impact induced loss of water occurs predominantly by cis 1,3-and 1,4- volving abstraction of a proximal proton by the oxygen atom (20). The expulsion of methanol from cyclohexyl methyl ethers has been shown to proceed by an identical process (8,21). However, one would predict 1,Celimination from the intact steroid i-methyl ether 2 to be precluded since the %-proton, being situated on the opposite face of the steroid from the 6P-methoxy group, is prohibited from approaching to within close proximity of the 6P-oxygen atom.…”

“…This fact, in labeled with deuterium specifically at carbon atoms conjunction with a recent report of the stereo -1,2, 3,4,7,8,9, and 19 (see Table 1). selective electron impact induced elimination of In every case the deuterated i-cholesteryl methyl methanol from arylcyclohexyl methyl ethers (8), ether, 2, was obtained from the correspondingly " I " " ( , I , , I , , , I I I I , I I I , I 8P-dl-, and 9cl-dl-cholesterol have been described in a previous paper from this laboratory (13). The 2,2,4,4-d, and 3a-dl analogs were prepared via the en01 acetate of 4-cholesten-3-one (13) by the procedure of Ockels and Budzikiewicz (14).…”

“…In alcohol moiety as a 3,5-cyclosteroid (4) during light of the recent report of stereoselective elaboration of the side chain (5,27). In addition, methanol elimination from cyclohexyl methyl these 3,5-cyclosteroids have proven valuable in re-ethers upon electron impact ionization (8), we were cent preparations of plant hormones (6) and A-nor interested in determining whether the expulsion of steroids (7). Although mass spectrometry plays a an ROH molecule from these 33-cyclosteroids invital role in the structure confirmation of inter-volved a site-and/or stereospecific hydrogen mediates in these syntheses, a systematic study of abstraction.…”

“…Such knowledge is essential for unequivocal structure elucidation by mass spectrometry and also bears on the current interest in the stereospecificity of electron impact induced eliminations. Deuterium labeling of carbon atoms 1,2,3,4,7,8,9, and 19 of6~-methoxy-3a,5-cyclo-5a-cholestane established the course of methanol extrusion and the identity of the highly diagnostic A ring cleavage ion Mt -55. Mechanisms are proposed for these key fragmentations.…”