Total Synthesis of (-)- and (+)-Botryodiplodin and (+)- and (-)-Epibotryodiplodin.

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Abstract
The title compounds were prepared by the conjugate addition (d.e. > 94%) of LiMe-CNCu to the chiral isoprene units (+)-(2R)- and (-)-(2S)-benzyloxy-2,5-dihydrofuran-4-carboxaldehyde (Ir and Is) followed by methylithium-attack on the mixture of aldehydes formed (3 and 4) and oxidation of the resulting mixture of alcohols (5 and 6) to give the ketones (-)-(2RS,3R,4R)- and (-)-(2R,3R,4S)-acetyl-2-benzyloxy-3-methyltetrahydrofuran (7r and 8r) and (+)-(2R,3S,4S)- and (+)-(2R,3S,4S)-4-acetyl-2-benzyloxy-3-methyltetrahydrofuran (7s and 8s), respectively. The ketones were separated and hydrogenolytic removal of the benzyl group of 8r, 8s, 7r, and 7s gave the title compounds, respectively. Epimerisation of (-)-botryodiploidin with aqueous sodium hydrogencarbonate gave a (racemic) mixture of (-)- and (+)-boytryodiplodin and (+)- and (-)-epibotryodiplodin. Treatment of bovine serum albumin and L-lysine with (-)-botryodiplodin gave an orange gel and a dark-red solution, respectively. This paper describes the experimental details for the synthesis of the two botryodiplodin enantiomers 10r and 10s and their epimers 9r and 9s. It also shows that (-)-botryodiplodin (10r) undergoes base-catalysed epimerisation at both carbons .alpha. to the carbonyl groups (ketone and aldehyde/hemiacetal), resulting in a racemic mixture containing all the title compounds. A preliminary account of part of this work has been reported.

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