Antibiotics U 1200Synthesis and Antibacterial Activities of (9S)-3-O-Descladinose-6-O-methyl--3-oxo-12-(Δ 2 -pyrazolinyl)-12-dehydroxy-21-demethyl-9-dihydroerythromycin A. -A 10-step synthesis of title compound (I) from clarithromycin is presented. This product is active against macrolide-sensitive S. aureus and Staphylococcus epidermidis in vitro and also shows a higher activity against macrolide-resistant S. aureus 5676 than erythromycin and clarithromycin. -(WANG, Y.-T.; HU, L.; CHEN*, W.-M.; HU, A.-X.; SONG, Q.-L.; GUAN, D.; Lett.