Clerodane diterpenes from the bark of Casearia tremula

Six novel clerodane diterpenes have been isolated from the bark of Casearia tremula. They were characterized by extensive use of Heteronuclear Multiple Bond Coherence NMR spectroscopy as rel-18(S),19(R)-diacetoxy-18,19-epoxy-6(R)-methoxy-2(S)-(2ξ-methylbutanoyloxy)5(R),8(S),9(S),10(R)-cleroda-3,13(16),14-triene, rel-18(S),19(R)-diacetoxy-18,19-epoxy-2(S)-(2ξ-methylbutanoyloxy)-5(R),8(S),9(S),10(R)-cleroda-3,13(16),14-triene, rel-18(S),19(R)-diacetoxy-18,19-epoxy-2(R)-hexanoyloxy-5(R),8(S),9(S),10(R)-cleroda-3,13(16),14-triene, rel-18(S),19(R)-diacetoxy-18,19-epoxy-6(R)-hydroxy-2(S)-octanoyloxy-5(R),8(S),9(S),10(R)-cleroda-3,13(16),14-triene and rel-18(S),19(R)-diacetoxy-18,19-epoxy-6(R)-hydroxy-2(S)-undecanoyloxy-5(R),8(S),9(S),10(R)-cleroda-3,13(16),14-triene, rel-18(S),19(R)-diacetoxy-18,19-epoxy-6(R)-hydroxy2(S)-(2ξ-methylbutanoyloxy)-5(R),8(S),9(S),10(R)-cleroda-3,13(16),14-triene and rel-18(S),19(R)-diacetoxy-18,19-epoxy-6(R)-hydroxy-2(S)-(3ξ-hydroxyoctanoyloxy)-5(R),8(S),9(S), 10(R)-cleroda-3,13(16),14-triene.