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971.
972.
973.
[structure: see text] Long-chain fatty acid enol ester 1 is the major metabolite of a new family of small molecules isolated from the heterologous expression of environmentally derived DNA. A versatile synthesis of 1, in which an aromatic acetaldehyde is O-acylated with a long-chain acyl chloride allowed for the rapid construction of both the isolated product (1) and a number of structural analogues (including 8, 17, and 18). 相似文献
974.
An efficient synthesis of 2,4-methanoproline from serine is described. The cyclobutane is formed by a sensitized intramolecular [2+2] photoaddition. 相似文献
975.
The preparation of -3a-aryl-4-oxo-decahydrocyclohepta[b]pyrroles and -3a-aryl-4-oxo-octahydroindoles is facilitated by using a cyanomethyl group to both protect nitrogen and serve as a precursor for a formaldehyde iminium ion. 相似文献
976.
Jon Baker 《Theoretical chemistry accounts》1985,68(3):221-229
Alternative definitions of bond order, valency, gross orbital populations and total atomic charge for SCF wavefunctions are compared. It is found that there are sound theoretical and numerical reasons for preferring definitions based on the Löwdin density matrix. 相似文献
977.
978.
979.
Electron diffraction data of dimethyl sulphate are interpreted by a 2:1 mixture of the C2 and C2v rotamers. This finding is also in agreement with the dipole moments of dimethyl sulphate and diethyl sulphate in benzene solution. The SO bond length and OSO bond angle are in agreement with the previously described empirical relationships. The variations in the O ?O distances in the different moieties OSO , OS-O, O-S-O, deserve special attention. 相似文献
980.
We examine the possibility of measuring the geometrical size of multiparticle processes. The mean-square impact parameter, 〈b2〉, of a process can be estimated by means of lower bounds which are determined from experiment. A bound of this type, which has been proposed by Webber, is found to be inadequate for the estimate. We propose several alternative bounds. One of them represents a considerable improvement over Webber's bound, with essentially no increase in the difficulty of the measurement. Another is a theoretically optimal bound which, however, requires an extremely high-statistics experiment. We also describe a method of deriving further bounds; and make estimates of the difference between the bounds and the true 〈b2〉. 相似文献