Some amino sugars structurally related to 6-deoxymannojirimycin precursors prepared from methyl 6-deoxy-2,3-O-isopropylidene-alpha-D-lyxo-hexofuranosid-5-ulose and methyl 2,3-O-isopropylidene-alpha-D-lyxo-pentodialdo-1,4-furanoside

Methyl (5S)-5-C-amino-5-cyano-5-deoxy-2,3-O-isopropylidene-alpha-D-lyxofuranoside has been synthesised from methyl 2,3-O-isopropylidene-alpha-D-lyxo-pentodialdo-1,4-furanoside, applying the Strecker synthesis. Analogously, methyl (5S) and (5R)-5-C-amino-5-cyano-5,6-dideoxy-2,3-O-isopropylidene-alpha-D-lyxo-hexofuranosides were prepared from methyl 6-deoxy-2,3-O-isopropylidene-alpha-D-lyxo-hexofuranosid-5-ulose. The 5-S configuration was unambiguously determined by single-crystal X-ray diffraction analysis of corresponding N-acetyl derivatives. Conformations of five-membered rings are discussed. The conversion of N-acetylated amino nitriles to N-acetylamino acid ethyl ester and amide, respectively, is also described.

Chiral 2,2'-bipyridine-type N-monoxides as organocatalysts in the enantioselective allylation of aldehydes with allyltrichlorosilane

[reaction: see text] The Sakurai-Hosomi-type allylation of aromatic and heteroaromatic aldehydes can be catalyzed by the new heterobidenate bipyridine monoxide PINDOX with high enantioselectivities. The sterochemical outcome is mainly controlled by the axial chirality in PINDOX, which in turn is determined by the annulated terpene units.

Synthesis and structure determination of some sugar amino acids related to alanine and 6-deoxymannojirimycin

(5'R)-5'-Methyl-5'-[methyl (4S)-2,3-O-isopropylidene-beta-L-erythrofuranosid-4-C-yl]-imidazolidin-2',4'-dione was synthesised starting from methyl 6-deoxy-2,3-O-isopropylidene-alpha-D-lyxo-hexofuranosid-5-ulose applying the Bucherer-Bergs reaction. Its 5'-R configuration was confirmed by X-ray crystallography. Corresponding alpha-amino acid-methyl (5R)-5-amino-5-C-carboxy-5,6-dideoxy-alpha-D-lyxo-hexofuranoside (alternative name: 2-[methyl (4S)-2,3-O-isopropylidene-beta-L-erythrofuranosid-4-C-yl]-D-alanine) was obtained from the above hydantoin by acid hydrolysis of the isopropylidene group followed by basic hydrolysis of the hydantoin ring. Total deprotection afforded 5-C-carboxy-6-deoxymannojirimycin. Analogously, methyl (5S)-5-amino-5-C-carboxy-5,6-dideoxy-alpha-L-lyxo-hexofuranoside and 5-C-carboxy-6-deoxy-L-mannojirimycin were prepared from the corresponding (5'S)-5'-methyl-5'-[methyl (4R)-2,3-O-isopropylidene-beta-D-erythrofuranosid-4-C-yl]-imidazolidin-2',4'-dione starting from methyl 6-deoxy-2,3-O-isopropylidene-alpha-L-lyxo-hexofuranosid-5-ulose.

Copper(II)-mediated oxidative coupling of 2-aminonaphthalene homologues. Competition between the straight dimerization and the formation of carbazoles

Whereas the Cu(II)-mediated oxidative coupling of 2-aminonaphthalenes 7a and 7b results in the clean formation of 1,1'-binaphthyls 13a and 13b, respectively, their higher homologues and congeners 8-12 have been found to exhibit a different reaction pattern. Thus, 2-aminoanthracene (8) gave a approximately 1:1 mixture of the expected bianthryl derivative 15 and the carbazole 16, whereas the 9-aminophenanthrene (10), 3-phenyl-1-aminonaphthalene (11), and 2-aminochrysene (12) produced almost exclusively the corresponding carbazoles 19, 20, and 21, respectively. By contrast, the isomeric 3-aminophenanthrene (9) gave rise to the azo compound 17 as a result of the preferential oxidation on the nitrogen. The carbazoles have been shown to arise directly from the coupling reactions rather than from the primarily formed binaphthyls. Alternatively, carbazole 19 can also be prepared from 1b on reaction with hydrazine. On the other hand, treatment of 3a with hydrazine resulted in the formation of a approximately 2:7 mixture of amine 11 and arylhydrazine 22. 2,2'-Diamino-1,1'-bianthryl (15) has been resolved into enantiomers via cocrystallization with (-)-N-benzylcinchonidinium chloride and shown to have (R)-(-)-15 configuration by X-ray crystallography.

Preparation and structure determination of two sugar amino acids via corresponding hydantoin derivatives

(4R)-2,3-O-Isopropylidene-methylspiro[4,6-dideoxy-alpha-L-lyxo+ ++-hexopyranosid-4,5'-imidazolidin]-2',4'-dione and (4R)-2,3-O-isopropylidene-methylspiro[4,6-dideoxy-beta-D-ribo-h exopyranosid-4,5'-imidazolidin]-2',4'-dione were prepared under various reaction conditions starting from methyl 6-deoxy-2,3-O-isopropylidene-alpha-L-lyxo-hexopyranosid-4-++ +ulose. Corresponding alpha-amino acids methyl (4R)-4-amino-4-C-carboxy-4,6-dideoxy-alpha-L-lyxo-hexopyranosid e and methyl (4R)-4-amino-4-C-carboxy-4,6-dideoxy-beta-D-ribo-hexopyranoside were obtained from the above hydantoins by selective acid hydrolysis of the isopropylidene group, followed by basic hydrolysis of the hydantoin ring. The crystal structures of both hydantoin derivatives are also presented.

Absolute configuration of a diaryldiacyloxy spiroselenurane and resolution of a carbon analog

The enantiomers of 3,3'-spirobi(3-selenaphthalide) (2) were obtained via direct separation by liquid chromatography on a chiral stationary phase. Determination of the absolute configuration was made by X-ray crystallography with the use of the anomalous dispersion technique. The first eluted (+)-form (lambda = 302 and 365 nm) of 2 was found to have (S)-configuration. By a comparison of CD-spectra, the same (S)-configuration could be assigned to the (+)-forms of the sulfur (1) and tellurium (7) analogs of 2. An asymmetric dichloro-substituted spirobilactone (4) was also synthesized and separated into its enantiomers. Relative configurations between 4 and its parent compound (3) were established from the corresponding chiroptical data obtained. Chirality 12: 71-75, 2000.

An Approach toward the Triquinane-Type Skeleton via Reagent-Controlled Skeletal Rearrangements. A Facile Method for Protection-Deprotection of Organomercurials, Tuning the Selectivity of Wagner-Meerwein Migrations, and a New Route to Annulated Lactones

Nonlinear triquinane-type building blocks have been synthesized using three strategic steps, namely, (1) Hg(2+)-mediated opening of a cyclopropane ring involving a skeletal rearrangement (3 --> 8), (2) an intramolecular organometallic addition across a C=O bond triggered by activation of the C-HgX group by means of Me(3)CuLi(2) (14 --> 26), and (3) selective, reagent-controlled skeletal rearrangements (43 --> 47 with Tl(3+) or Hg(2+); 43 --> 51 + 52 with Pd(2+); 44 --> 47 with Pd(2+)). A new method for protection/deprotection of organomercurials has been developed, which allows selective reduction of a carbonyl group with NaBH(4) and other hydrides (8 --> 14 --> 16 --> 20) and Tebbe methylenation (14 --> 31 --> 32). Oxidative demercuration (8 --> 11 + 28) and Pd(2+)-catalyzed carbonylation of organomercurials (20 --> 53) allowed syntheses of gamma- and delta-lactones.