Total synthesis of natural product marmycin A was studied. An expeditious synthetic strategy for the key fragment 8-amino-3-methylbenz[a]anthraquinone (1) was established with decarboxylative alkylation, Pd(OAc)(2)-catalyzed cyclization, aromatization, and C-N coupling as the key steps. However, final assembly of marmycin A was hampered by the failure to obtain the carbohydrate fragment 2. Instead, a small library of desmethyl analogues of marmycin A was prepared in moderate yields by using the InBr(3)-catalyzed C- and N-glycosidation reaction. The absolute configuration of these compounds was confirmed by comparison of their spectroscopic data with that reported for marmycin A, and by X-ray analysis.

A three-step, one-pot tandem reaction including radical nucleophilic alkylation/cyclization/ aromatization was developed using 0.3 equivalents of silver(I) acetate (AgOAc) as the catalyst and 2 equivalents of ammonium persulfate [(NH 4 ) 2 S 2 O 8 ] as the oxidant. This strategy is highly efficient for the assembly of pentacyclic complex carbazoles from aryl-fused bromobenzoquinones and indol-3-ylpropanoic acid acids in 52-72% overall yields (three steps). This new approach provides a significant improvement over the previously reported methods and would greatly facilitate analog library construction of pentacyclic complex carbazoles and benefit further biological evaluation of these compounds.

Six new triterpenoid glycosides, gynosaponins I–VI (1–6, resp.), together with three known compounds, ginseng Rb1 (7), gypenoside XLIX (8), and gylongiposide I (9), were isolated from the aerial parts of Gynostemma pentaphyllum. Based on ESI‐MS, IR, 1D‐ and 2D‐NMR data (HMQC, HMBC, COSY, and TOCSY), the structures of the new compounds were determined as (3β,12β,20S)‐trihydroxydammar‐24‐ene 20‐O‐[α‐rhamnopyranosyl‐(1→2)]‐β‐glucopyranoside (1), (3β,12β,20S)‐trihydroxydammar‐24‐ene 20‐O‐[α‐rhamnopyranosyl‐(1→2)] [α‐rhamnopyranosyl‐(1→3)]‐β‐glucopyranoside (2), (3β,12β,20S)‐trihydroxydammar‐24‐ene 3‐O‐β‐glucopyranosyl‐20‐O‐[α‐rhamnopyranosyl‐(1→2)]‐β‐glucopyranoside (3), (3β,12β,20S)‐trihydroxydammar‐24‐ene 3‐O‐β‐glucopyranosyl‐20‐O‐[α‐rhamnopyranosyl‐(1→2)] [α‐rhamnopyranosyl‐(1→3)]‐β‐glucopyranoside (4), (3β,12β,20S)‐trihydroxydammar‐24‐ene 3‐O‐{[β‐glucopyranosyl‐(1→2)]‐β‐glucopyranosyl}‐20‐O‐[α‐rhamnopyranosyl‐(1→2)]‐β‐glucopyranoside (5), and (3β,12β,20S)‐trihydroxydammar‐24‐ene 3‐O‐{[β‐glucopyranosyl‐(1→2)]‐β‐glucopyranosyl}‐20‐O‐[α‐rhamnopyranosyl‐(1→2)] [α‐rhamnopyranosyl‐(1→3)]‐β‐glucopyranoside (6).