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The intramolecular cycloaddition of 5 yields the unsaturated lactones 17a, 17b, and 17c as three major isomeric adducts. These were further reduced to the corresponding derivatives 21a, 21b, and 21c, which are intermediates for the synthesis

The signals from spongy bone on gradient echo sequences depend on the fat and water proton content as well as the differences in magnetic susceptibility at the border between the trabeculae and the bone marrow. From the signal intensities for different echo times, signal modulation was quantified by a special algorithm and at the same time the T2 relaxation time was calculated. Using a fat-water phantom, it was shown that the product of the initial fat and water signal intensity (modulation coefficient) is applicable to indicate the extent of signal modulation and thereby the chemical shift and, moreover, to indicate changes in the fat/water ratio sensitively. In 16 individuals of different ages (23 to 64 years, average 42.4 years) there was a tendency for the T2 relaxation time from the spongiosa of lumbar vertebrae to increase with age, this can be explained by a reduction in the trabecular content, causing reduction in the magnetic inhomogeneity of the bone marrow. The results indicate the usefulness of the sequence and the mathematical model for evaluating the spongy bone in cases of osteoporosis and of malignant haematological disorders.

Detailed analysis of the proton and carbon‐13 NMR spectra of cyclo(l‐prolyl‐l‐N‐methylphenylalanyl) in chloroform and methanol in relation to its nonmethylated analog provided information on the conformation of the title compound in solution as well as on the effect of N‐methylation and solvation. The N‐ray structure of the title compound in the crystalline state showed the same conformational features as the solution structure. The phenyl group folds over the diketopiperazine ring which resembles a flattened half‐chair. Both amide bonds are considerably nonplanar. The pyrrolidine ring of proline shows a strong pucker at the ring junction with the largest χ5 value hitherto observed.