Douglas E.A. Rivett

The Structure and Synthesis of Tsitsikammafuran: A New Furanosesquiterpene from a South African Dysidea Sponge

Abstract Three furanosesquiterpenes, the new tsitsikammafuran (1) and the known nakafurans-8 (2) and -9 (3) were isolated from a South African Dysidea sponge. The structure of tsitsikammafuran, initially proposed as 3-[(furan-3-yl)methyl]-p-cymene, from a combination of biosynthetic arguments and the available spectroscopic data, was unequivocally confirmed by the synthesis of 1 from thymol. The synthesis of two regioisomers of tsitsikammafuran, 4-[(furan-3-yl)methyl]-m-cymene (4) and 2-[(furan-3-yl)methyl]-p-cymene (22), from p-cresol and 2-bromo-2-nitrocamphane respectively, further supported the structural assignment of 1.

Synrotolide, an α-pyrone from Syncolostemon rotundifolius

Abstract The structure of synrotolide, a new α-pyrone isolated from Syncotostemon rotundifolius, has been established as 6R-[3R,6S-(diacetyloxy)-4R,5S-(dihydroxy)-1-heptenyl]-5,6-dihydro-2H-pyran-2-one. Oleanolic acid is the major component of both S. rotundifolius and S. densiflorus.

5,6-Dihydro-α-pyrones from Syncolostemon argenteus

Abstract The chemical structures of five new α-pyrones, synargentolides A-E, isolated from Syncolostemon argenteus , have been established as 6 R -[4 R ,5 R ,6 S -triacetyloxy-1 E -heptenyl]-5,6-dihydro-2H-pyran-2-one, 6 R -[5,6 S -diacetyloxy-1,2-dihydroxy-3 E -heptenyl]-5,6-dihydro-2H-pyran-2-one, 6 R -[5,6 S -diacetyloxy-1,2-dihydroxy-3 E -heptenyl]-5 S -acetyloxy-5,6-dihydro-2H-pyran-2-one, 6 R -[5,6 S -diacetyloxy-1,2-dihydroxy-3 E -heptenyl]-5-hydroxy-5,6-dihydro-2H-pyran-2-one and 6 S -[4,6 S -diacetyloxy-1,5-dihydroxy-2 E -heptenyl]-5 S -acetyloxy-5,6-dihydro-2H-pyran-2-one, respectively, based on spectral chiroptical and chemical evidence.

Stereochemical studies on boronolide, an α-pyrone from Tetradenia barberae

Abstract The structure of boronolide isolated from Tetradenia barberae has been confirmed as 6 R -[1 R ,2 R ,3 S -(trisacetyloxy)-heptyl]-5,6-dihydr

Structure of the 5,6-dihydro-α-pyrone, umuravumbolide

Abstract The structure and absolute stereochemisry of umuravumbolide and desacetylumuravumbolide have been elucidated by spectral means.

The absolute stereochemistry of a diterpene from Ballota aucheri.

The semi-synthetic transformation of hispanolone, isolated from Ballota africana, into 6beta-hydroxy-15,16-epoxylabda-8,13(16),14-trien-7-one has established an ent-labdane absolute stereochemistry for a diterpene metabolite originally isolated from B. aucheri.

The structure of euryopsol, a furanoeremophilane from Euryops species

Abstract Euryopsol, isolated from the resin of Euryops spp., has been shown to be 1α,6β,10β-trihydroxyfuranoeremophilane. Euryopsol, C15H22O4, m.p. 173–174°, occurs together with euryopsonol, C15H20O3, m.p. 230–231°, in the unsaponifiable fraction of the resin of Euryops floribundus (Compositae).1* We have also obtained the former from E. tenuissimus.

The structure of euryopsonol

Abstract Euryopsonol, isolated from the resin ofEuryops floribundus, has been shown to be 3α-hydroxy-9-oxofuranoeremophilane.

Absolute configuration of α-pyrones from Cryptocarya latifolia and Syncolostemon densiflorus

The stereochemical structures of two α-pyrones previously isolated from Cryptocarya latifolia have been shown to be 6R-[2R,4S,6S-(triacetoxy)-heptyl]-5,6-dihydro-2H-pyran-2-one and 6R-[2S,4S-(diacetoxy)-pentyl]-5,6-dihydro-2H-pyran-2-one. Syndenolide from Syncolostemon densiflorus is 6R-[5S-(acetoxy)-1R,2R,3S-(trihydroxy)-heptyl]-5,6-dihydro-2H-pyran-2-one.

5,6-Dihydro-α-pyrones from Syncolostemon parviflorus

The chemical structure and absolute stereochemistry of three new α-pyrones, synparvolides A-C, isolated from Syncolostemon parviflorus, have been established respectively as 6R-[5S,6S-(diacetyloxy)-1R,2S-(epoxy)-3S-(hydroxy)-heptyl]-5,6-dihydro-2H-pyran-2-one, 6R-[1Z,5S,6S-(diacetyloxy)-3S-(hydroxy)-1-heptenyl]-5,6-dihydro-2H-pyran-2-one and 6R-[6S-(acetoxy)-1R,3S-(dihydroxy)-2R,5R-(epoxy)-heptyl]-5,6-dihydro-2H-pyran-2-one, based on spectral, chiroptical, and chemical evidence.