i
Epimer Forms in Nitrite Photolysis C—O bond unexpectedly shifts position during reaction of nitrite to oximino alcohol The carbon-oxygen bond can change configuration during a nitrite-to-oximino alcohol reaction. This unexpected finding was made by Dr. Alex Nickon, Dr. J. R. Mahajan, and Dr. F. J. McGuire of Johns Hopkins University, Baltimore, Md. The group made the discovery while probing the structure of W-caryophyllene alcohol, C 1 5 H 2 6 0 . The nitrite-oximino alcohol reaction (C&EN, April 25, 1960, page 50) involves photochemical rearrangement of a nitrite ester. A hydroxyl group forms during the reaction, and an oximino group replaces two hydrogens. The reaction is valuable in synthesis and structural studies. Formerly, no change of configuration of the C—O bond was observed in the reaction. The Johns Hopkins chemists, however, uncovered a case with "a"-caryophyllene alcohol, in which the C—O bond does change position during the nitrite reaction to produce an epimer. The Johns Hopkins group used the nitrite-oximino alcohol reaction as a degradative step [/. Org. Chem., 26, 3617 (1961)]. A ketone that contains no enolizable hydrogens is obtained from "a"-caryophyllene alcohol ("a"-alcohol). Infrared data show that a strained carbonyl, comparable to that in a fivemembered ring, is present in the ketone. Hydrogenation of the ketone over platinum gives the same "a"-alcohol and a liquid, isomeric alcohol
(epi-"a"-alcohol). Oxidizing the epi"a"-alcohol with chromium trioxide reforms the original ketone. These experiments show that "a"-alcohol and epi-"a"-alcohol are epimeric secondary alcohols. Nitrosation of epi-'W-alcohol with sodium nitrite in acetic acid gives the crude epi-nitrite as a liquid from which epi-'W-alcohol can be regenerated by saponification. Irradiating the epi-nitrite in benzene solution with a mercury lamp gives an oximino alcohol. Acid hydrolysis of the oximino alcohol provides the corresponding keto alchohol. Wolff-Kishner reduction of the keto alcohol to epi-"a:"alcohol shows that the same carbon skeleton is present. Nitrosation of the "a"-alcohol with sodium nitrate in acetic acid gives the corresponding nitrite. The nitrite reverts to "a"-alcohol on saponification. Irradiating the nitrite produces the same oximino alcohol as is obtained from the epi series. This work shows that in the photorearrangement of "a"-caryophyllene alcohol nitrite, the carbon-oxygen bond undergoes change from its original configuration to the epi configuration. This finding should caution others using the nitrite-oximino alcohol reaction in proof-of-structure work, Dr. Nickon says. When the reaction is used as a means of identification, the possibility of epimerization must be realized, and the reaction product must be carefully examined.
C - 0 Bond in 'V'-Nitrite Changes Position
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An automatic analyzer for mass screening for certain types of cancer is now in experimental use. It is faster, cheaper, and more accurate than its human counterpart. Called a "cytoanalyzer," the machine consists of a television-like unit combined with a microscope to record characteristics of human cells. Data collected by the camera are passed on to a computer for analysis. The cytoanalyzer is designed specifically to examine cells from cervical and vaginal smears for early indications of cancer, Dr. E. G. Diacumakos and Dr. Emerson Day of the Sloan-Kettering Institute for Cancer Research, and M. J. Kopac of New York University told the New York Academy of Sciences' conference on Scanning Techniques in Biology and Medicine. Two of the cytoanalyzers are currently in experimental use. One is at Sloan-Kettering and the other at the U.S. Public Health Service in Hagerstown, Md. In mass screenings for cancer, the machine is expected to perform in less than an hour the number of examinations that would require a cytologist a full day. Since the cytoanalyzer is subject to neither fatigue nor distractions, it is more accurate than a cytologist, the scientists say. In present practice, the cytologist quickly inspects each smear, then closely examines those showing cancer possibility. When the cytoanalyzer is used, it performs the initial screening to select the smears that the cytologist will study in more detail. Widespread use of cytoanalyzers should do much to improve the effectiveness of mass cancer detection programs and reduce costs, the Sloan-Kettering and USPHS workers say.
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