Crystal structure of isozygosporin A p-bromobenzoate

The structures of diisopropyl 9,9'-bifluorenylidene-1,1'-dicarboxylate and 9,9'-bifluorenylidene

“…These different orientations are probably due to crystal packing effects and may explain the slight differences in the angles between the fluorenylidene planes in the two molecules. The bond lengths and angles within the isopropoxycarbonyl fragments are close to those found in similar compounds, with the exception of the C(14)-O(1) single bonds, for which the average length is 1.35 A, rather more than for equivalent bonds in propargyl 2bromo-3-nitrobenzoate (1.31 A) (Calabrese, McPhail & Sim, 1966) and isozygosporin A p-bromobenzoate (1.32 A) (Tsukuda & Koyama, 1972), but less than that in 9,10-anthrohydroquinone dibenzoate (1.39 A) (Iball & Mackay, 1962).…”

The structure of chaetoglobosin A: a novel use of quartet invariants

“…All H atoms were found and the structure was refined by a blocked least-squares approach, with isotropic thermal parameters for the H atoms and anisotropic parameters for the others, to an R factor of 0.033. While it was expected that the absolute stereochemistry of chaetoglobosin A would be similar to that of the 11-cytochalasins to which it is chemically related and whose absolute configuration is known (Tsukuda & Koyama, 1972;Buchi, Kitaura, Yuan, Wright, Clardy, Demain, Glinsukin, Hunt & Wogan, 1973), there is no direct evidence and, therefore, both possible enantiomers were refined using anomalous-scattering factors for C, N and O. The expected enantiomer gave the lower R factor but the difference was not significant.…”

Biosynthesis of Cytochalasans. Part 6. The Mode of Incorporation of Phenylalanine into Cytochalasin D

“…This process is a trans-elimination of the elements of ammonia with stereospecific loss of the 3-@o(S)-proton of phenylalanine [6] [8a]4). Phenylpyruvic acid (4) (shown in its enol form) is the normal biogenetic precursor of phenylalanine, and is 2) 3) Phenylalanine and phenylpyruvic acid labelled with [4'-3H]-are radiochemically unstable and some error (ca. 5%) is introduced by decomposition [5].…”