Transformation of the 7-isopropylidene group in 5-dethia-5-oxacephams
2001; Elsevier BV; Volume: 57; Issue: 7 Linguagem: Inglês
10.1016/s0040-4020(00)01098-x
ISSN1464-5416
AutoresRobert Łysek, Z. Urbańczyk-Lipkowska, Marek Chmielewski,
Tópico(s)Marine Sponges and Natural Products
ResumoAbstract [2+2]Cycloaddition of CSI to 5-O-protected-3-O-allenyl-1,2-O-isopropylidene-α- d -xylofuranoses 8 and 9 gave respective β-lactams 10–13 having an exo-propylidene group, in moderate stereoselectivity. Compounds 10, 11 and tetracyclic cephams 14, 15 obtained from 10 and 11 or 12 and 13, were used as substrates for a variety of transformations leading to the introduction of isopropyl, hydroxyisopropyl, oxygen and nitrogen functions, α to the β-lactam carbonyl group. These reactions proceeded in high stereoselectivity with control of the absolute configuration of the cephams formed.
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