Nigel Ramsden

Inhibition of HIV replication by amino-sugar derivatives

The plant alkaloids castanospermine, dihydroxymethyldihydroxypyrrolidine and deoxynojirimycin have recently been shown to have potential anti‐HIV activity [(1987) Proc. Natl. Acad. Sci. USA 84, 8120–8124; (1987) Nature 330, 74–77; (1987) Lancet i, 1025–1026]. They are thought to act by inhibiting α‐glucosidase I, an enzyme involved in the processing of N‐linked oligosaccharides on glycoproteins. We report here the relative efficacy of a spectrum of amino‐sugar derivatives as inhibition of HIV cytopathicity. Several α‐glucosidase inhibitors and α‐fucosidase inhibitors were found to be active at concentrations which were non‐cytotoxic.

Practical synthesis of deoxymannojirimycin and mannonolactam from L-gulonolactone. Synthesis of L-deoxymannojirimycin and L-mannonolactam from D-gulonolactone

Abstract An eight step synthesis of deoxymannojirimycin from L-gulonolactone in 25% overall yield is reported the key step is the formation of a δ-lactam by the reduction of a 5-azidolactone. The preparations of mannonolactam front L-gulonolactone and of L-deoxymannojirimycin and L-mannonolactam from D-gulonolactone are described.

Two alexines [3-hydroxymethyl-1,2,7-trihydroxypyrrolizidines] from Castanospermum australe

Abstract Two new alexines have been isolated from Castanospermum australe . The structure of 1,7a-diepialexine was firmly established by X-ray crystallographic analysis of the corresponding 1,7-isopropylidene derivative. The structure of the second new alexine was tentatively assigned as 7,7a-diepialexine or its enantiomer. The abilities of naturally occurring alexines to inhibit mouse gut disaccharidase and fungal glucan 1,4-α-glucosidase are compared.

Synthesis of, and lack of inhibition of a rhamnosidase by, both enantiomers of deoxyrhamnojirimycin and rhamnolactam: β-mannosidase inhibition by δ-lactams

Abstract Synthesis of both enantiomers of deoxyrhamnojirimycin and rhamnonolactam from D- and L-gulonolactones are described. The effects as inhibitors of the enantiomeric deoxyrhamnojirimycins and rhamnonolactams on human liver glycosidases are compared with deoxymannojirimycin and mannonolactam. No significant inhibition of the activity of naringinase (an α-L-rhamnosidase) was caused by any of these compounds.

A practical synthesis of deoxymannojirimycin and of (2s,3R,4R,5R)-3,4,5-trihydroxypipecolic acid from D-glucose

Abstract Deoxymannojirimycin [1,5-dideoxy-1,5-imino-D-mannitol] may be prepared in moderate amounts in an overall yield of 35% in ten steps from diacetone glucose; the key step is formation of the piperidine ring by intramolecular nucleophilic displacement of a triflate at C-2 of a methyl glucofuranoside by a nitrogen function at C-6, irrespective of the anomeric configuration of the sugar. A synthesis of (2S,3R,4R,5R)-3,4,5-trihydroxypipecolic acid is reported.

Synthesis of 6-epicastanospermine and 1,6-diepicastanospermine from L-gulonolactone and synthesis of L-6-epicastanospermine and L-1,6-diepicastanospermine from D-gulonolactone

Abstract The syntheses of the natural product 6-epicastanospermine [(1S,6R,7R,8R,8aR)-1,6,7,8-tetrahydroxyoctahydroindolizine], isolated from Castanospermum australe, and of 1,6-diepicastanospermine [(1R,6R,7R,8R,8aR)-1,6,7,8-tetrahydroxyoctahydro-indolizine] from L-gulonolactone and the synthesis of the enantiomers, L-6-epicastanospermine [(1R,6S,7S,8S,8aS)-1,6,7,8-tetrahydroxyoctahydroindolizine] and L-1,6-diepicastanospermine [(1S,6S,7S,8S,8aS)-1,6,7,8-tetrahydroxyoctahydro-indolizine] from D-gulonolactone are reported.

Short syntheses of D-deoxymannojirimycin and D-mannonolactam from L-gulonolactone and of L-deoxymannojirimycin and L-mannonolactam from D-gulonolactone

Abstract Short syntheses of D-deoxymannojirimycin and of D-mannonolactam from L-gulonolactone are reported; identical sequences on D-gulonolactone lead to L-deoxymannojirimycin and L-mannonolactam.

Synthesis of the enantiomers of 6-epicastanospermine and 1,6-diepicastanospermine from d- and l-gulonolactone

The synthesis of the enantiomers of 6-epicastanospermine and of 1,6-diepicastanospermine from the enantiomeric gulonolactones is reported and the structure of the former is established as (1S,6R,7R,8R,8aR)-1,6,7,8-tetrahydroxyoctahydroindolizine. The inhibitory activities of the diastereomers against the amyloglucosidase-catalysed hydrolysis of p-nitrophenyl alpha-D-glucopyranoside were investigated, and the effects of 6-epicastanospermine and of 1,6-diepicastanospermine on 14 human liver glycosidases are reported.

δ-Lactams: synthesis from D-glucose, and preliminiary evaluation as a fucosidase inhibitor, of L-fuconic-δ-lactam

Polyhydroxylated δ-lactams are a potential class of glycosidase inhibitors; the synthesis of L-fuconic-δ-lactam (7), which preliminary studies have shown to be a weak but specific α-L-fucosidase inhibitor, is described.

SAR studies around a series of triazolopyridines as potent and selective PI3Kγ inhibitors.

Herein we describe the SAR of a novel series of 6-aryl-2-amino-triazolopyridines as potent and selective PI3Kγ inhibitors. The 6-aryl-triazolopyridine core was identified by chemoproteomic screening of a kinase focused library. Rapid chemical expansion around a bi-functional core identified the key features required for PI3Kγ activity and selectivity. The series was optimized to afford 43 (CZC19945), a potent PI3Kγ inhibitor with high oral bioavailability and selectivity over PI3Kα and PI3Kδ. Modification to the core afforded 53 (CZC24832) which showed increased selectivity over the entire kinome in particular over PI3Kβ.