Chemoenzymatische „Chiral‐Pool”︁‐Synthese von (+)‐exo‐Brevicomin aus Kohlenhydraten mit Fructose‐1,6‐diphosphat‐Aldolase

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Abstract
Chemoenzymatic “Chiral‐Pool” Synthesis of (+)‐exo‐Brevicomin from Carbohydrates Using Fructose 1,6‐Diphosphate AldolaseFructose‐1,6‐diphosphate aldolase (EC 4.1.2.13) catalyzes the stereospecific aldol reaction between 1,3‐dihydroxyacetone phosphate (4) and 5‐oxohexanal (3) or its 5‐dithiane‐protected analog 8. The products of the aldol reactions are dephosphorylated with acid phosphatase (EC 3.1.3.2). Whereas the aldol adduct of 3 cyclizes spontaneously to give the bicyclic brevicomin precursor 3, the adduct of 8 first has to be deprotected with sulfuryl chloride and wet silica gel. The resulting bicyclic α‐hydroxy ketone 3 is reduced with LiAlH4 to form the 1,2‐diol 14 which is then deoxygenated to give the vinyl compound 17 by treatment of the corresponding dixanthate 15 with tributyltin hydride or by treatment of the corresponding mesylate 16 with sodium naphthalenide. The olefin 17 is finally converted to (+)‐exo‐brevicomin (1) by hydrogenation with diimide.