W. David Ollis

Heterocyclic mesomeric betaines

Article de synthese traitant du classement de ces composes et de leurs reactions de cycloaddition

Stereoselective epoxidation of hydroxyenones. The synthesis of the sidechain of clerocidin

Abstract The sidechains of clerocidin 1 and terpentecin 2 contain a unique chiral assembly [C 5 H 5 O 4 ]. Models for the stereospecific synthesis of this structural feature are reported.

The orthosomycin family of antibiotics—I : The constitution of flambamycin

Abstract The antibiotic, flambamycin, is shown to have the novel oligosaccharide structure ( 1 ) associated with two orthoester linkages. It is proposed that flambamycin ( 1 ), the everninomicins ( 28 ), curamycin, avilamycin, destomycin A ( 29a ), destomycin C ( 29b ), destomycin B ( 30 ), hygromycin B ( 29c ), the antibiotics A-396-I (29d) and SS-56C ( 29e ), belong to a new family of antibiotics called the orthosomycins.

Asymmetric metal-catalysed epoxidation of electron-deficient olefins

Abstract The SYN diastereospecific epoxidation of acyclic β-hydroxyketones (β-hydroxyacrylates) and cyclic β-hydroxyketones using titanium and vanadium catalysts is reported. Some initial results on the asymmetric epoxidation of these systems using the Sharpless titanium-tartrate catalyst are also described.

Absolute configurations of isoflavans

Abstract The absolute configurations of isoflavans and isoflavanquinones isolated from Cyclolobium, Dalbergia and Machaerium species were established by comparison of their ORD curves with that of (3S)-5,7,3′,4′-tetra-methoxyisoflavan and (3S)-7,4′-dimethoxyisoflavan-2′,5′-quinone, respectively. The assignments were checked by the ozonolysis of the isoflavan (−)-duartin to (R)-paraconic acid and the oxidation of isoflavans to isoflavanquinones. The PMR spectra of the dihydropyran ring of the isoflavans are discussed in terms of the preferred conformation of this ring.

Pterocarpans from Dalbergia spruceana

Abstract The wood of Dalbergia spruceana contains, besides O-acetyloleanolic acid, elemicin and 3,4,5-trimethoxy-cinnamaldehyde; the neoflavonoids (S)-4-methoxydalbergione and dalbergin; the isoflavones biochanin-A, formononetin, pseudobaptigenin and caviunin; and the pterocarpans (±)-medicarpin, (±)-maackiain, as well as the 3,4-dihydroxy-, 3-hydroxy-4-methoxy- and 4-hydroxy-3-methoxy-derivatives of (6aR,11aR)-8,9-methylenedioxypterocarpan. The constitutions of the three last named compounds were deduced by spectra and confirmed by synthesis of (±)-4-hydroxy-3-methoxy-8,9-methylenedioxypterocarpan.

On the metal-catalysed epoxidation of electron-deficient olefins

Abstract The SYN diastereoselective epoxidation of β-hydroxyacrylates and cyclic β-hydroxyketones using the Sharpless titanium and vanadium catalysts is reported. The first kinetic resolution of these systems is also described.

Preparation and Cycloaddition Reactions of Novel Heterocyclic Mesomeric Betaines

Abstract The heterocyclic mesomeric betaines 6a–c reacted with dimethyl acetylenedicarboxylate and ethyl propiolate giving the 1,3-dipolar cycloaddition products 7a–c and 8a–c, respectively. With esters of maleic, fumaric, acrylic and methacrylic acids, mesomeric betaines 6a and 6b gave substituted tetralone derivatives.

Vestitol and vesticarpan, isoflavonoids from Machaerium vestitum

Abstract The wood of Machaerium vestitum contains the previously described O -acetyloleanolic aldehyde, formononetin, (+)-medicarpin, and (−)-mucronulatol, besides (+)-vestitol [(3 S )-7,2′-dihydroxy-4-methoxyisoflavan] and (+)-vesticarpan [(6 aS ,11 aS )-3,10-dihydroxy-9-methoxypterocarpan]. The constitutions of vestitol and vesticarpan were deduced by spectra and confirmed by syntheses.

Mucronulatol, mucroquinone and mucronucarpan, isoflavonoids from Machaerium mucronulatum and M. villosum

Abstract Additionally to the cinnamylphenols described in a previous paper, wood samples of Machaerium mucronulatum and M. villosum contain isoflavones, besides (−)-duartin, (−)- and (±)-mucronulatol [(3 S )- and rac-7,3′-dihydroxy-2′,4′-dimethoxyisoflavan], (−)-mucroquinone [(3 S )-2-methoxy-5-(7-hydroxy-8-methoxychroman-3-yl)-1,4-benzoquinone] and (+)-mucronucarpan [(6a S ,11a S )-2,10-dihydroxy-3,9-dimethoxypterocarpan]. The constitutions of mucronulatol, mucroquinone and mucronucarpan were deduced by spectra and degradations, and confirmed by syntheses.