Phaeochromycins F–H, three new polyketide metabolites from Streptomyces sp. DSS-18

• Jian Li,
• Chun-Hua Lu,
• Bao-Bing Zhao,
• Zhong-Hui Zheng and
• Yue-Mao Shen

Beilstein J. Org. Chem. 2008, 4, No. 46, doi:10.3762/bjoc.4.46

• -chromen-5-yl)methyl]-2-oxo-2H-pyran-3-yl}methyl)-2-oxo-2H-pyran-6-yl]methyl}-2-methyl-4H-chromen-4-one, named phaeochromycin F. Phaeochromycin G (2) was isolated as an amorphous powder. Its molecular formula was determined as C13H12O3 based on HR-ESI mass spectra and NMR data. The IR absorption at 1660 cm

• -chromen-5-yl)methyl]-2-oxo-2H-pyran-3-yl}methyl)-2-oxo-2H-pyran-6-yl]methyl}-2-methyl-4H-chromen-4-one 1), brown, amorphous powder. UV (MeOH): 301.5; [α]D20 = 0 (c = 0.5, CHCl3); IR (KBr): 3424, 2974, 1653, 1391, 1089, 1050; 1H and 13C NMR: see Table 1; HR-ESIMS: m/z 603.1282 ([M + Na]+; calc. 603.1267

Synthesis of 2,6-trans- disubstituted 5,6-dihydropyrans from (Z)-1,5-syn-endiols

• Eric M. Flamme and
• William R. Roush

Beilstein J. Org. Chem. 2005, 1, No. 7, doi:10.1186/1860-5397-1-7

• elimination could be increased up to 99:1 for substrates 11a, 11d, and 11f. All other substrates examined also showed improved selectivity for pyran formation, and in all cases the dihydropyran ent-3 was obtained in at least 72% yield. In summary, the scope of cyclodehydration reactions of (Z)-1,5-syn-diols 2

Methods for the synthesis of polyhydroxylated piperidines by diastereoselective dihydroxylation: Exploitation in the two-directional synthesis of aza-C-linked disaccharide derivatives

• Andrew Kennedy,
• Adam Nelson and
• Alexis Perry

Beilstein J. Org. Chem. 2005, 1, No. 2, doi:10.1186/1860-5397-1-2

• exploited in the two-directional synthesis of aza-C-linked disaccharide analogues. A two-directional oxidative ring expansion was used to prepare bis-enones such as (2R,6S,2'S)-6-methoxy-2-(6-methoxy-3-oxo-3,6-dihydro-2H-pyran-2-ylmethyl)-1-(toluene-4-sulfonyl)-1,6-dihydro-2H-pyridin-3-one from the