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Brianolide (1), a new antiinflammatory diterpenoid of the briarein class, possessing a beta substituent at C-12 (R), has been isolated from the Okinawan gorgonian Briareum sp. Its structure has been established from spectral data in conjunction with a single crystal X-ray analysis.

In order to elucidate the hydrogen-bonding behavior of cross-linked resin-bound peptides in the swollen state, conformational properties of cross-linked polystyrene resin bound oligoleucines were studied by infrared spectroscopy. The conformational analysis of H-Leu"-Phe-resins ( = 3, 6, 9, and 15) swollen in methylene chloride revealed that the peptide chains had various conformations depending on the chain length: = 3, essentially an unordered structure; = 6 and 9, mainly the /3-sheet structure; and = 15, predominantly the -helical structure. The formation of the /3-sheet structure indicates that cross-linked resin-bound peptides in the swollen state can easily interact with each other through intermolecular hydrogen bonds even at a low loading of peptide chains and that the intraresin site separation of the peptide chains is not achieved even when the peptide chain length is not so long. Effects of solvent polarity on conformational transformations of H-Leu"-Phe-resins ( = 3, 6, 9, and 15) were also examined. Cross-linking effects on the conformational properties of cross-linked H-Leu"-Phe-resins ( = 3, 6, 9, and 15) were further investigated by comparison with the conformational properties of soluble H-Leu"-Phe-resins ( = 3, 6, 9, and 20).

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ABSTRACT:Cross-linked and soluble polystyrene resin-bound oligo(leucine)s were prepared by the step-by-step coupling of Boc-Leu3 -0H to H-Phe-resins using dicyclohexylcarbodiimide and 1-hydroxy-IH-benzotriazole. The solid state conformational analysis of HfLeu 3 j,Phe-resins (n = 1-5, cross-linked resin; n = 1-3, soluble resin) by infrared spectroscopy indicated that the peptide chains had various conformations depending on the chain length: n =I, essentially an unordered conformation; n = 2--4, mainly the jl-structure; and n = 5, predominantly the a-helix. The formation of the jl-structure indicates that resin-bound peptide chains can easily interact with each other through hydrogen bonds even in polymer networks. The correlation of the conformation in the swollen state with that in the solid state was examined using various solvents. Effects of shear stress on conformational transformations of HfLeu 3 j,Phe-resins (n = 1-3) was also examined.