H.-P. Wessel

Syntheses of the chromomycinone side chain from carbohydrate precursors

Abstract Appropriate dithiane derivatives of D-threo configuration were prepared starting with D-arabinose and D-galactose, respectively. Their dianions served for nucleophilic additions to model aldehydes, thus comprising syntheses of the complex side chain of chromomycinone. In contrast to former reports a trianion formation of a dithiane-blocked α,β-dihydroxy aldehyde could not be confirmed.

Synthesen von Emodinaldehyd [1] / Synthesis of Emodine Aldehyde [1]

9 By chromium trioxide oxidation and subsequent acid hydrolysis triacetyl emodine (3) was transferred to the aldehyde in a two-step synthesis. In a more favourable sequence 3 was reacted to the bromomethyl derivative 4 and this solvolyzed to the citreoroseine derivative 5. A second NBS reaction gave 8 which after acid hydrolysis led to emodine aldehyde (9). This five-step process proceeded without chromatographic separation in 27% overall yield.