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Derek Horton

Publications and source records attributed to Derek Horton.

8 recordsLinked to original sources
PubMed2006

Synthesis of 3'-C-substituted thymidine derivatives by free-radical techniques: scope and limitations.

The scope and limitations of radical-mediated 3'-C-substitution of pyrimidine nucleosides was evaluated with 5'-O-(tert-butyldimethylsilyl)thymidine or its tert-butyldiphenylsilyl analogue having thionoester or thionoamide groups at O-3', including (methylthio)thiocarbonyl, (phenoxy)thiocarbonyl, (pentafluorophenoxy)thiocarbonyl, and (1-imidazolyl)thiocarbonyl. Their reaction with acrylonitrile, methyl acrylate, and allyltributyltin under radical-generating conditions affords corresponding 3'-C-alkylated products, together with the product of simple deoxygenation at C-3'. The conditions for optimizing the yield of 3'-C-substituted product are presented.

Free Radicals↗
PubMed2006

Synthesis and reactivity of nonstabilized diazo sugars.

1,6-Anhydro-4-deoxy-4-diazo-2,3-O-isopropylidene-beta-D-lyxo-hexopyranose (4) is a stable crystalline compound readily accessible by an improved synthetic procedure. It has been used as a model for evaluating the reactivity of the diazo group, when not stabilized by an adjacent carbonyl function, in a rigid chiral matrix. A range of carbene-type, electrophile-promoted, and 1,3-dipolar reactions were evaluated, leading to 4,4'-alkene dimers, 4-deoxy-3-enose and related derivatives, 4,4-dihalo compounds, 4-spirocyclopropane derivatives, 4-spiropyrazole structures, and by skeletal rearrangement, branched-chain anhydropentose structures having a bicyclo[2.2.2] skeleton.

Azo Compounds↗
PubMed2006

Anthracycline glycosides of 2,6-dideoxy-2-fluoro-alpha-L-talopyranose.

The methyl beta-glycoside of the title sugar, obtained from 2-deoxy-2-fluoro-beta-D-glucopyranose tetraacetate by a sequence with detailed characterization of all intermediates, was converted by acetolysis-bromination into 3,4-di-O-acetyl-2,6-dideoxy-2-fluoro-alpha-L-talopyranosyl bromide, coupling of which with (7S,9S)-4-demethoxydaunomycinone afforded the 3,4-diacetate of 4-demethoxy-9-O-(2,6-dideoxy-2-fluoro-alpha-L-talopyranosyl)daunomycinone (19). The antitumor-active 19 was converted by way of its 14-bromo derivative into the 14-hydroxy analogue, the antitumor-active 4-demethoxyadriamycinone glycoside 21.

Anthracyclines↗
PubMed2006

Studies on enolization of aldehydo-aldose derivatives.

Acetylation of the 2,3-O-isopropylidene derivative (1) of D-glyceraldehyde with hot acetic anhydride in the presence of sodium acetate give a mixture of (Z)- and (E)-enol acetates (2 and 3), together with the acetylated racemic aldehydrol (4) of 1. Likewise, the acyclic aldehydo 2,3:4,5-diisopropylidene acetals of D- and L-arabinose, D-xylose, and D-ribose underwent conversion into enol acetates, with the (Z) isomers preponderating, and convertible photochemically into the corresponding (E) isomers. Under other conditions of acetylation, the aldehydo derivatives were converted into the corresponding aldehydrol diacetates.

Acetylation↗
PubMed2006

A synthetic route to 9-(polyhydroxyalkyl)purines.

Mercuric-ion promoted condensation of 6-chloropurine with acetylated dimethyl dithioacetals of D-ribose and D-arabinose in nitromethane afforded a separable mixture of 1'(S)-2,3,4,5-tetra-O-acetyl-1-(6-chloropurin-9-yl)-1-S-methyl-1-thio-D-ribitol (4) and its 1'(R) diastereomer, and the corresponding 1'(R)-arabinitol analogue (5); the structure of 4 was confirmed by X-ray crystallography. Desulfurization of 4 and 5 by tributylstannane in toluene gave 2,3,4,5-tetra-O-acetyl-1-(6-chloropurin-9-yl)-1-deoxy-D-ribitol (7) and the arabinitol analogue 8, convertible by the action of thiourea into the 1,6-dihydro-6-thioxopurin-9-yl analogues 9 and 10, which on deacetylation furnished the corresponding acyclic-sugar nucleosides 11 and 12.

Arabinose↗
PubMed1996

Cycloaddition of Cyclopentadiene to 3-Deoxy-1,2:5,6-di-O-isopropylidene-alpha-D-erythro-hex-3-enofuranose. Synthesis and Representative Chemistry of 1,6-Anhydro-2,3-dideoxy-beta-D-glycero-hex-2-enopyran-4-ulose ("Isolevoglucosenone").

Treatment of D-glucose-derived alkene 4 with cyclopentadiene in the presence of a Lewis acid results in the formation of cycloaddition products 8-11. Evidence is presented to show that these 1,6-anhydro sugar-cyclopentadiene adducts do not arise from rearrangement of 4 to isolevoglucosenone (5) followed by cycloaddition but are the result of Lewis acid-catalyzed rearrangement of alkene 4 to acyclic dienophile 12 followed by addition of cyclopentadiene. Major cycloadduct 8 has been utilized as a source of the enantiomerically pure carbocycles 14-25 by manipulation of the alkene and ketone functions and cleavage of the 1,6-anhydro bridge. In the absence of diene, alkene 4 undergoes rearrangement to enone 5 in 32% yield. Reaction of 5 with several dienes results only in the formation of "bottom-face" adducts 10,11, 28, and 29, and conjugate addition of either HN(3) or Me(3)COOH is found to be completely stereoselective to afford 30 and 31, respectively. Subsequent manipulation of azide 30 leads to precursors of several naturally occurring 2-amino-2,3-dideoxy sugars.

Journal Article↗