RESEARCH
greatest interest because of their biological activity, based on rat studies, are:
configuration is reached via acid hydrolysis.
• 6 a-fluorohydrocortisone—Upjohn finds this one to b e the most active singly substituted glucocorticoid (liver glycogen deposition activity) that doesn't cause salt retention. Glucocorticoid activity is about 1 2 times that of the parent steroid, says Hogg. • 6 a-fluoroprednisolone — S y n t e x ' s work with anti-inflammatory activity, says Djerassi, shows that this steroid is the most potent one. And while Upjohn reports insignificant salt retention, Syntex finds that the steroid actually causes salt excretion. Glucocorticoid action is about 80 times that of hydrocortisone, says Hogg. • 6 a, 9 a-difluoroprednisolone—reported by Upjohn only. The steroid is by far the most active glucocorticoid yet, Hogg claims—about 400 times more active than hydrocortisone. Salt retention with the steroid is measurable, but Hogg says that the compound's other potency may veto this mineral activity.
fluorinated compounds, although they grabbed the spotlight, weren't the only steroids that came to light during the symposium. Reaching deeper into his bag of steroids, Djerassi came up with two more prizes. One is the first reported synthesis of equilin, a strong estrogen found in mare's urine. The second prize is a new synthetic path to certain 19-nor steroids, noted for their anabolic and progestational properties.
• Other Steroids, Too.
The
new
Surface Counts Alcoa probes effect of surface treatment on resinbonded joints
A L C O A researchers are working to fill a void in the knowledge of how surface treatment affects the strength of resinbonded joints between *.ietals and between metals and nonmetals. To begin with, Alcoa's Mike Miller Both groups find that 6 a-fruorination says that if maximum strength is not the jacks up progestational, androgenic, major factor, a solvent or vapor deand corticoid properties of representa- greased surface is usually adequate. tive members among these three major But for "structural" adhesives, those endocrine classes. which develop shear strengths over ^Synthetic Routes. Both ap- 2500 p.s.i., chemical pretreatment is proaches to the new fluoro steroids g o vital, Miller told the 32nd National Colthrough a 5,6-epoxy stage vising per- loid Symposium at the University of Ilacetic acid. Upjohn researchers form linois. What type pretreatment is best the epoxide from methyl pregna-4,17- depends both on the adhesive and on (20)-diene-3,l l-dione-21-oate, obtained the intended use for the joint. in previous work. This epoxy derivaOne example: Alcoa tested a sandtive is then fluorinated at carbon-6 with wich of natural rubber bonded between hydrogen fluoride—result is a 6 beta- two pieces of aluminum with a phefluoro substituent. In a series of steps, nolic-rubber adhesive. Pretreating the hydrocortisone's typical D ring "super- aluminum surfaces with a phosphoric structure" is put in, and aqueous acid acid-alcohol solution gives a fivefold hydrolysis changes the 6 beta-fluoro t o increase in tensile strength compared to 6 alpha. To get the prednisolone com- solvent degreasing treatment. In genpound, 6 alpha-fluorohydrocortisone is eral, Alcoa finds that acid stabilized surput through Upjohn's standard micro- faces give better tensile shear strengths biological transformation to get Ci-C 2 than surfaces pretreated with alkaline unsaturation. solutions. The Syntex method, says Djerassi, Also, Alcoa compared phenolic-polystarts with cortisone. The trick is to vinyl formal and phenolic-polyvinyl acetylate both the 17 alpha and the 2 1 butyral adhesives. With the formal adbeta hydroxy groups to protect them hesive, simple degreasing is just as efduring subsequent reaction without fective as a sulfuric—chromic acid treatforming an enol acetate in ring A. In ment. But with butyral adhesive, acid more common steroid reactions, only treatment gives a marked improvement the 21-hydroxyl is protected this way. in joint strength. After acetylation, the 5,6-epoxide is And, says Miller, an electroplated aluformed, followed by fluorination with minum surface apparently isn't as good boron trifluoride. This reaction gives as an unplated surface. For example, a 6 beta-fluoro product, too. Proper the strength of a phenolic-polyvinyl 52
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butyral adhesive on plain aluminum treated with a phosphoric acid-alcohol solution is greater than with silver, tin, and lead electroplated surfaces; failures turned up between the adhesive and electroplate. Miller cautions that the initial strength of a bond isn't the only thing to be considered. Often, a joint with high initial strength won't stand up as well in actual service as a bond that is weaker to begin with. For j** stance, the initial tensile strength c. resinbonded joints with chromate primed surfaces is lower than with chemically treated surfaces since bond strength is determined by metal-to-primer adhesion. However, Alcoa finds that chromate pre-priming greatly extends the life of the joint when it's exposed to corrosive environments. Unprimed panels failed after three months in synthetic sea water, while the test samples, with a chromate primer, showed very little decrease in bond strength even after six months' exposure.
Laundering Reactor Fuel Liquid fused-salt fuel systems get reprocessed by ionic reactions in melt A . NEW molten uranium-fuel mixture, to be tested soon in pilot scale, will permit continuous removal of fission products from the fuel through fused-salt reactions. One of the biggest practical problems in nuclear reactors is the job of reprocessing the fuel. In solid-fuel systems this is particularly troublesome because of handling necessary to prepare the material for re-use. Homogeneous, self-moderating liquid-fuel systems offer possibilities of continuous automatic scavenging. Best liquid-fuel combination for this type of high temperature reactor consists of a uranium salt dissolved in a molten fluoride medium, Warren R. Grimes of Oak Ridge told the 11th Annual Summer Symposim at the General Electric Research Laboratory in Schenectady co-sponsored by the ACS Division of Analytical Chemistry and the journal, Analytical Chemistry. This basic melt is a eutectic combination of lithium and beryllium fluorides melting at about 1000° F. Into the mixture h e dissolves uranium tetrafluoride as fuel. During critical operation, a wide
