Pinguisane-Type Sesquiterpenes from the South American Liverwort Porella recurva (Taylor) Kuhnemann
The chemical composition of a dichloromethane extract of the South American liverwort Porella recurva has been examined. Two new pinguisane-type norsesquiterpenoid natural products were isolated: 6,11-epoxy-15-nor-3,4-dioxo-5,10-pinguisadien-12-acetate and 6,11- epoxy-15-nor-4-oxo-5,10-pinguisadien-12-acetate. In addition two known pinguisane-type sesquiterpenes were also isolated: norpinguisone and norpinguisone methyl ester. All structures were elucidated by means of NMR spectroscopic techniques and mass spectrometry.
Chemosystematics of Marchantiophyta
On the basis of morphological characteristics, liverworts have been divided into the Marchantioid group or “complex thalloids”, and the Jungermannioid group, which comprises two morphological subgroups, “simple thalloids” and “leafy hepatics”. These groups have been defined in the hierarchy of most classification schemes and have long been viewed as natural phylogenetic units (167, 732). The recent molecular phylogenetic studies have brought new insights to the systematics of liverworts and have greatly modified this morphology-based concept (337, 665). The new classification of the Marchantiophyta proposed by Crandall-Stotler and coworkers (168, 169) is presented in Table 1.1. Each underlined genus has been studied chemically previously.
Interaction of Formaldehyde and Tetrahydrofolic Acid and Its Relation to the Enzymic Synthesis of Serine
Interaction of Formaldehyde and Tetrahydrofolic Acid and Its Relation to the Enzymic Synthesis of Serine