Antibiotics, antitumour macrolide

Macrolides and Related Compounds. - Complex phosphonates continue to be used in the construction of carbon skeletons and in cyclisation reactions, as exemplified by the synthesis of didesepoxyrhizoxin, the biogenetic precursor of the antitumour agent rhizoxin, via intramolecular olefination of (225). (+)-Trienomycins A and F, members of a family of ansamycin antibiotics, have been synthesised using a double Wittig reaction of the diphosphonium salt (226) as a key step. The reaction produces a mixture of isomers including 21% of the required (all- ) product. 

The new antitumour antibiotic pyrrolosporin A (11) is a macrolide with an unusual spiro-a-acyl tetronic acid moiety. It also contains a 4-amino-2,4,6-trideoxy-P-D-aru6mo-hexopyranose unit, a sugar not previously found in nature (see Vol. 24, p. 148-9 for the synthesis of this sugar in studies of antibiotic analogues), and methanolysis of pyrrolosporin A gave the methyl a-pyranoside, with the pyrrole unit still linked to the sugar. 

Macrolide antibiotic. Isol. from Amphidinium sp. Shows antitumour props. Amorph. [a] —45° (c, 1 in CHCI3). 21-Epimer Amphidinolide D C32H50O8 M 562.742... 

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