Petra Wagner

Moenomycin A - Structure-activity relations synthesis of the D-galacturonamide analogue of the smallest antibiotically active degradation product of moenomycin A

Abstract Compound 10c which is the galacturonamide analogue of 2, the smallest degradation product of moenomycin A (1) with full antibiotic activity, has been synthesized. 10c is devoid of antibiotic activity.

Dynamic 77se nmr of phenylselenyl cyclohexane derivatives

Abstract For phenylselenyl cyclohexane ( 1 ) ring inversion barriers (ΔG ≠ 278 of 11.7 ± 0.2 (eq- 1 → ax- 1 ) and 10.5 ± 0.2 kcal/mol (ax- 1 → eq- 1 ) and an A-value of 1.1 were determined. Extraordinarily large diamagnetic γ effects of ca 30–40 ppm per CH 2 group were found.

Spectroscopic properties of 6-hydroximino-5β-cholestane derivatives

Abstract The structures of 18 and the CD data of 13 6-hydroximinocholestane derivatives are presented. Oxime configurations were determined by1H and13C NMR spectroscopy. An X-ray analysis of11 has been performed.

Unusual behaviour of 2,2-dimethyl-2H-chromene derivatives (precocenes) in phenylselenenylation

Treatment of 2,2-dimethyl-2H-chromene derivatives (precocenes)(1) with benzeneselenenyl chloride in methylene dichloride solution affords a mixture of unusual phenylselenenylation products (7), (8), and (9) instead of the expected addition derivatives (3). In the case of 6-unsubstituted chromenes (1a,d,e), C-6 aromatic substitution (phenylselenenylation) takes place also.

Spiroforskolin: Structure and mode of formation

Abstract Forskolin ( 1a ) rearranges BF 3 -mediated to the spiro compounds 12a and 13 . It is assumed that 12a and 13 are formed via cationic intermediate 18 .