Reduction Of 2b Research Articles

Novel enantiomerically pure 2-amino-1,4-diols from chiral 4-hydroxymethyl-5-iodo-1,3-oxazin-2-ones

Reduction of (4 S,5 S,6 S)-4-hydroxymethyl-5-iodo-6-methyl-1,3-oxazin-2-one 2a and (4 S,5 S,6 R)-4-hydroxymethyl-5-iodo-6-phenyl-1,3-oxazin-2-one 2b with tributyltin hydride in ethanol afforded 1,3-oxazin-2-one 3a and 1,3-oxazolidin-2-one 4b , respectively. Hydrolysis of 3a and 4b under basic conditions led to enantiomerically pure aminodiols 1a and 1b . Reduction of 2b in refluxing toluene led to the unexpected bicyclic tetrahydrofuro[3 a, d]-1,3-oxazolidin-2-one 5 as the sole product.

A Convenient One Step Synthesis of trans‐Artemidin and Tetrahydrocapillarin.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of a ‘direct-linked’ C-disaccharide from a pyranulose glycoside

Syntheses of five ‘direct linked’ C-disaccharides 8a–e were reported. The (Et 3SiH/BF 3·Et 2O) reduction of pyranulose glycoside 1 yielded (6 S)- and (6 R)-6-(2,3,5-tri- O-benzoyl-β- d-ribofuranosyl)pyran-3(2 H,6 H)-one ( 2a and 2b) in a ratio of ca. 2:1 and in 88% combined yield. The absolute stereochemistry of each was determined from its CD spectrum. The reduction of 2a with NaBH 4 in methanol afforded two allylic alcohols 6a and 6b in 14 and 73% yield, respectively. The reduction of 2b with NaBH 4 afforded 6c and 6d in 30 and 56% yield, respectively. Cis hydroxylation of the double bond in compounds 6a–d with osmium tetroxide gave 7a–e. The stereoisomers 7a–e were separated and their configuration was established by 1H NMR spectroscopy. Debenzoylation of compounds 7a–e with aqueous sodium carbonate produced deprotected C-disaccharides 8a–e.

Synthesis and reactions of some new substituted spirofurochromanone derivatives

Condensation of different cyclic ketones with visnaginone 1a and khellinone 1b afforded spirofurochromanone derivatives 2a-f. Compounds 2a and 2b were readily demethylated to give the compounds 3a and 3b. Nitration of 2b and 2e gave the nitrofurochromonone and quinone derivatives 4 and 5 respectively. The chroman-4-ol derivatives 6a and 6b were obtained from reduction of 2b and 2e which were directly dehydrated to give compounds 7a and 7b respectively. Also, amide 6c was prepared which failed to provide 6d on acid hydrolysis. Bromination of the chromene 7a gave the corresponding 9-bromo derivative 7c and failed to give compound 8. Treatment of 2b with NBS afforded the corresponding 2,9-dibromo derivative 10. The chromanones 2b and 2e were reacted with hydroxylamine, phenyl hydrazine, aniline and paraformaldehyde to give the products 11a-e and 12a,b.

Synthesis of the Preininger‐Alkaloid and its Enantioselective Reduction to Macrostomine

AbstractThe Preininger‐alkaloid, dehydro‐normacrostomine (2b, Scheme 1) was synthesized starting from rac. α‐acetyl‐3,4‐dimethoxybenzylcyanide (3) (Scheme 2). The key intermediate 4‐acetyl‐6,7‐dimethoxy‐1‐(3,4‐methylene‐dioxybenzyl)isoquinoline (11) is converted via a Mannich base to the nitrile 17 (Scheme 7) which in turn is cyclized to the Preininger‐alkaloid (2b) by careful hydrogenation. ‐ Reduction of 2b with a modified Iwakuma‐reagent, followed by N‐formylation and subsequent LiAlH4‐reduction produced (R)‐(+)‐macrostomine (enantiomer of 1) in 72% optical purity.