Mitsuhiro Kinoshita

A novel synthesis of 2-deoxy-α-glycosides

The key step of the synthesis involves the reaction of glycals [3,4,6-tri-O-acetyl-D-glucal (1), the new glycal derivative 4-O-acetyl-1,5-anhydro-2,6-dideoxy-3-C-methyl-3-O-methyl-L-ribo-hex-1-enitol (2), and 3-acetamido-4,6-di-O-acetyl-1,5-anhydro-2,3-dideoxy-D-arabino-hex-1-enitol (3)] with 1.5 molar equivalents of several alcohols in the presence of N-bromosuccinimide in acetonitrile to give mainly the corresponding 2-bromo-2-deoxy-alpha-glycopyranosides (4--21). The glycopyranosides (4-8 and 16-21) from 1 and 3 have the alpha-D-manno configuration and those (10--15) from 2 have the alpha-L-altro configuration. The yields are high from 1, virtually quantitative from 2, and moderate from 3. Debromination of the 2-bromo-2-deoxy compounds with tributylstannane and a radical initiator gives the corresponding 2-deoxy-alpha-glycopyranosides (22-38) in quantitative yields. In particular, the branched-chain glycal 2 reacts with alcohols to give exclusively the corresponding alpha-glycopyranosides (27--32) of cladinose in strikingly high overall yields. The stereoselectivity and regiospecificity of the bromination reaction are described. 1,3-Dibromo-5,5-dimethylhydantoin and N-bromoacetamide are also found to be useful for the reaction.

Total synthesis of tylonolide, an aglycone of tylosin

Abstract The total synthesis of tyionolide, a 16-membered-ring aglycone of a macrolide antibiotic, tyiosin, has been accomplished by coupling two segments of C1-C10 and C11-C17 portions, which are stereospecifically derived from D-glucose.

Total synthesis of elaiophylin (azalomycin B)

Antibiotic elaiophylin 1a has been first synthesized by a convergent route involving aldol condensation between (5R,6R,7R)-5-0-[2′-deoxy-3′,4′-di-0-(dimethylisopropylsilyl)-α-L-fucopyranosyl]-6-ethyl-7-0-(diethylisopropylsilyl)-5,7-dihydroxy-3-octanone 3a and (7S,8S,15S, 16S) - (3E, 5E, 11E, 13E) -8,16-bis [ (1 ′R) -1′ -formylethyl] -7,15-dimethyl-1, 9-dioxacyclohexadeca-3,5, 11,13-tetraene-2,10-dione 4, followed by desilylation. The segments, 3a and 4, were synthesized from D-glucose and 2-deoxy-L-fucose.

Total synthesis of carbomycin B and josamycin (leucomycin A3)

Abstract The stereospecific total synthesis of macrolide antibiotics, carbomycin B and josamycin (leucomycin A 3 ), is described. The key aglycone has been synthesized by coupling two segments of C1–C10 and C11–C16 portions, which are stereospecifically derived from glucose.

Stereospecific total synthesis and absolute configuration of a macrocyclic lactone antibiotic, A26771B

Abstract The total synthesis of a sixteen-membered macrocyclic lactone antibiotic, A26771B and its absolute configuration are described by using D-glucose as a chiral source.

Enantiospecific synthesis of C20C28 segment of concanamycin A: Application of diethylisopropylsilyl protecting group

A complex C20C28 segment5 of concanamycin A (1) has been first synthesized without side reactions by effective de-O-silylation of2a, which was constructed from the ethyl ketone3 by glycosidation with the fluoride4.

Synthetic studies of erythromycins. III. Total synthesis of erythronolide a through (9s)-9-dihydroerythronolide A

Abstract Erythronolide A ( 1 ) was enantiospecifically synthesized through (9S)-9-dihydroerythronolide A ( 2 ) from the chiral C-10-C-13, C-7-C-9, and C-1-C-6 synthetic segments, 3 , 5 , and 4 , respectively. The overall yield of 1 from 4 was 1.84% in 21 steps.

The total synthesis of rifamycin W

Abstract The first total synthesis of rifamycin W (1) has been accomplished by coupling two segments of the aliphatic ansa-chain 40 and the aromatic chromophore 12. The totally enantiospecific sequence elucidates the configurations of the C28 position and the C12 - C29 double bond to be R and E, respectively.

Total synthesis of tylosin

Abstract Tylosin has been synthesized byregio- and stereoselective introduction of the amino disaccharide moiety and D-mycinose onto the previously synthesized 16-membered-ring aglycone.

The diethylisopropylsilyl group: a new protecting group for alcohols

Abstract The diethylisopropylsilyl (DEIPS) group which is a new protective group for alcohols has been first characterized. DEIPS group can be distinguished from t-butyldimethylsilyl, triethylsilyl, tetrahydropyranyl groups and 2-deoxy glycoside with high selectivity in removing under mild acidic condition, although DEIPS group has high stability to many useful organic synthetic reaction conditions.