Peter Brown

The isolation of loliolide from an Indian Ocean opisthobranch mollusc.

In 1938 l lanske reported (2) a neutral substance obtained from F u mar ia oficiizalis (Papaveraceae) that was eventually shown to be the monoterpene loliolide isolated from the perennial ryegrass Lo1,iLm peretiiie (Graminae) and nicely assigned structure 1 by Hodges in 1964 (3). Subsequently loliolide has been identified in 14 other higher plant species representing a total of 13 familiec (table 1. variety of related substances ( l i ) . Similarly, photolysic of the zeaxanthin diepoxide (violaxanthin) from yellonpansies (V;oLa /r,color) yields a mixture containing loliolide (18). Both zeasmthin and violaxanthin are ubiquitous carotenoid pigments and may certainly account, in part, for loliolide formation in some plant species. Furthermore, even mild nickel (IT) oxide oxidation of flavoxanthin and chry-

Isolation and structural elucidation of 3,6-dioxo-hexahydro-pyrrolo [1,2-a]-pyrazine from the echinodermLuidia clathrata

Es wird über die Isolierung und Charakterisierung der Titelverbindung (Gly-l-Pro Lactam, I) aus dem SeesternLuidia clathrata berichtet. Die Kristallstruktur dieses Dioxopiperazinderivats wurde ermittelt. Der Piperazinring liegt in der Wannen-Konformation vor.

Structural Biochemistry 14. Permethylation of Nucleosides

Abstract Prominent molecular ions are generally observed in the field ionization (FI) mass spectra of unprotected nucleosides.2 In the one exception so far observed, that of guanosine, we found the simple methyl derivative, N2,N2-dimethylguanosine, to afford an easily detectible molecular ion. The electron impact (EI) mass spectrum of N2,N2-dimethylguanosine also displayed a molecular ion and suggested that nucleoside methyl derivatives might be more easily studied by EI methods. For this purpose and the more important objective of developing methods for sequencing small nucleic acid units by computer assisted3 FI-EI mass spectrometry, a program was initiated (1967) to explore permethylation of nucleosides. We believe protection by permethylation to be superior to pertrimethylsilylation and acetylation principally for reasons involving molecular weight and stability. Concurrently it was anticipated that such nucleoside methylation studies would afford routes to partially mathylated nucleosides of value in...

Bufadienolides-19. 3β-acetoxy-15-oxo-5β,14β-bufa-8,20,22-trienolide

Abstract Reaction of 3β - hydroxy - 14α,15α - epoxy - 5β - bufa - 20,22 - dienolide ( 1a ) with 72% perchloric acid was found to yield 14β - artebufogenin ( 2a ), 14α - artebufogenin ( 2b ), 15α - hydroxy-bufalin ( 3a ), and a new substance 3β,15ξ - dihydroxy - 5β,14ξ - bufa - 8,20,22 - trienolide ( 4a ). Similar results were realized by antimony (III) chloride and an iron(III) chloride catalyzed ring opening of epoxide 1a . Selective acetylation of the new bufadienolide ( 4a ) followed by oxidation completed a route to the title substance.

Structure of the bufadienolide bufotalin

Mass spectral and 1H n.m.r. evidence, coupled with degradation of bufotalin to 3β-acetoxybufotalien (II), in turn prepared by total synthesis, provide unequivocal support for the assignment of structure (I) to bufotalin.

A compact inexpensive gas chromatograph/mass spectrometer silicone rubber membrane separator

This interface should prove especially pertinent for those having a mass spectrometer and a gas chromatograph but unable to purchase a combination GC/MS instrument.