Chemical modification of erythromycin A: Synthesis of the C1–C9 fragment from erythromycin A and reconstruction of the macrolactone ring

Synthesis and Antibacterial Activity of a Novel Class of 15-Membered Macrolide Antibiotics, “11a-Azalides”

“…16,17 However, chemical modification at the C13 position has been underexplored because of its lack of chemical reactivity. During the mid 1990s, Waddell 18,19 and Nishida 20 independently reported C9-C13 modified EM-A derivatives, synthesized from the original C1-8 or 9 fragment of EM-A and a newly prepared C9 or 10-13 fragment. Although this "cut and paste" methodology seemed to be a universal procedure to provide structural diversity into the C13 region, the reported compounds were limited to simple and primitive derivatives.…”

“…The increasing prevalence of macrolide-resistant pathogens among clinical isolates in recent times is of concern to public health. − To overcome resistance problems, numerous chemical modifications of EM-A have been attempted. − In a chemobiosynthesis report seeking novel scaffolds by transformation of the macrolactone skeleton, the C13 position of EM-A promises to play a key role in the improvement of antibacterial activity against resistant pathogens. , However, chemical modification at the C13 position has been underexplored because of its lack of chemical reactivity. During the mid 1990s, Waddell , and Nishida independently reported C9−C13 modified EM-A derivatives, synthesized from the original C1−8 or 9 fragment of EM-A and a newly prepared C9 or 10−13 fragment. Although this “cut and paste” methodology seemed to be a universal procedure to provide structural diversity into the C13 region, the reported compounds were limited to simple and primitive derivatives.…”

Enhancement of enzyme activity and enantioselectivity via cultivation in nitrile metabolism by Rhodococcus sp. CGMCC 0497

“…These works are now under way. The results presented here demonstrate that of the many methods to improve enzyme activity and enantioselectivity, such as medium engineering [22], lipid coating [23], immobilization [24], genetic engineering [25] and chemical modification [26], optimization of culture conditions remains a facile and feasible way to enhance enzyme enantioselectivity as well as activity.…”

Phosphorylated aldehydes: Preparations and synthetic uses

“…They were prepared by treatment of a C 7 dialdehyde, protected at one extremity (double bond or tert-butyldimethylsilyl (TBS) ether), with the dimethyl 1-lithiomethylphosphonate at -80°C in THF, which gave the β-hydroxyphosphonates in 74-79% yield. Subsequent oxidation (PDC/DMF 102 or TPAP/NMO/CH 2 Cl 2 103,104 ) produced the corresponding β-ketophosphonate in excellent overall yield. Generation of the terminal aldehyde at C 9 was performed by oxidation of the primary alcohol with TPAP/NMO 103…”