Announcing . .. An ACS Summer Institute for College Teachers
Science plore the upper limits of detection by their technique, although larger se quences may be amenable to analysis. They say they would accept samples from academic investigators and private firms for such sequence analyses. Their work in this field has been supported by the National Institute of General Medical Sciences, the National Science Foundation, and the Robert A. Welch Foundation. D
that the 12,637 ± 10 mass ion they detected was a dimer of the dodecanucleotide they used, associated with four sodium atoms. In addition to the parent dodecanucleotide mass 6301 ± 3 ion, they also saw a mass at 8709 ± 8, which they conclude is a fragment of the dimer. The Texas A&M workers say no one has yet sent them a synthetic sequence longer than 18 bases, so they have not had a chance to ex
Aldol modification yields high optical purities June 21-30,1981 At Syracuse University, Syracuse, New York Partially supported by a grant from the ACS Education Commission The Institute will feature lec ture and hands-on laboratory experience with microcompu ters and related devices. Regis tration will be limited to the first 39 applicants. WHO SHOULD ATTEND The Institute is designed for col lege chemistry teachers who are computer novices—particular ly faculty of two- or four-year colleges or university faculty whose primary responsibility i$ undergraduate teaching.
Asymmetry in mandelic acid derivative
COSTS The tuition fee is $50.00. All meals, at a cost of $119.00 per participant, will be provided at a Syracuse University dining facility. Lodging is available either at a university dormitory or at a nearby motel.
For example, in work with post doctoral students William Choy and Francis A. J. Kerdesky and graduate student Barbara Imperiali, Masamune hydrogenated an optical isomer of majidelic acid to the cyclohexylhydroxyacetic acid, which gave 1cyclohexyl-l-hydroxy-2-butanone with ethyllithium, and then a 1-tertbutyldimethylsilyloxy derivative on silylation. To activate the propionyl group in these compounds for the aldol reac tion, the MIT workers treated the compounds with dicyclopentylborinyl or 9-borabicyclo[3,3,l]nonan-9-yl trifluoromethanesulfonates (triflates) to form dialkylborinylenolates. They carried out the aldol condensation with such aldehydes as propionaldehyde, desilylated the adduct with hydrogen fluoride, and oxidized to /3-hydroxy-a-methyl acid products. Yields were 70 to 85%, and optical purities ranged from 93 to more than 99%. D
Optical purities of almost 100% result from a method of carrying out aldol reactions developed by organic chemistry professor Satoru Masamune and his coworkers at Massa chusetts Institute of Technology [J. Am. Chem. Soc, 103, 1566 (1981)]. Their technique could ease laboratory production of such natural products as large-ring antibiotics. The group already has applied the method to making the erythromycin derivative 6-deoxyerythronolide B, whose total synthesis had been achieved earlier by collaborators of organic chemistry professor Elias J. Corey of Harvard University (C&EN, July 10,1978, page 25). In work supported by the National Institutes of Health, the MIT group made a dialkylborinylenolate of a mandelic acid derivative. The com mercial availability of either optical isomer of mandelic acid at $1.35 to $1.75 per gram adds attraction to the synthesis.
?(CH )
3 3
CH 3 CH,
Hs
CH,3s
J3Si(CH 3 ) 2
(Or ΥΌ C
+
OS02CF3—*
Active ketone
Borinyl trifflate
H'
~HO) V - ' H T)Si(CH 3 ) 2 C(CH3)3 Borinylenolate
gives almost 100% optical purity in products TO REGISTER For a descriptive flyer and reg istration form, write or call the Education Department, Ameri can Chemical Society, 1155 Six teenth Street, N.W., Washing ton, DC 20036; telephone 202872-4508.
24
C&EN April 27, 1981
Ç(CH3)3 CH3
CH3CH2CHO «
Propionaldehyde
w
CH3CH2
Η V C
OH
Ο
CH,
OSi(CH3)2 C
CH,CH
» C \ !/ iv C A C0 2 H OH
Active acid 70 to 85% yield >99% optical purity
