A Two-Step Approach to a Hexacyclic Lamellarin Core via 1,3-Dipolar Cycloaddition of Isoquinolinium Ylides to Nitrostilbenes

Abstract

The 1,3-dipolar cycloaddition reaction of isoquinolinium ylides to nitrostilbenes provides an approach to 1,2-diarylpyrrolo­[2,1-a]­isoquinolinium-3-carboxylates and then to a complete hexacyclic lamellarin core.

Toward “E‐Ring‐Free” Lamellarin Analogues: Synthesis and Preliminary Biological Evaluation

“…Additionally, to assess the impact of the E‐ring and extend the series of biologically active lamellarin analogues with a complete hexacyclic core, we prepared 5 a – 5 d using previously described synthetic procedure (Figure 3). [21] The characterization of 5 a – 5 c was consistent with the literature (Figures S12–S14). The structure of previously undescribed compound 5 d was confirmed by 1 H and 13 C NMR spectroscopy (Figures S15‐S16) and ESI‐MS, and its purity was confirmed by elemental analysis.…”

“…We exploited several previously described synthetic procedures using Ag 2 CO 3 in THF, [17] Et 3 N in CHCl 3 , [18] 2,6-lutidine-Cu(OAc) 2 system in DCE [19] and in DMSO, [20] and DABCO-MnO 2 system in toluene . [21] However, in all cases a mixture of a minor amount of the desired product of [3 + 2]-cycloaddition 3 and a major amount of compound 3' has been obtained. Two compounds were separated by recrystallisation from MeOH (3) with additional chromatographic purification of the mother liquor (3').…”

“…Pyridinium ylides 1 and 1 a , [25] nitrostilbenes 2 and 2 a – 2 c [24a,26] have been synthesized according to the described methods. Compounds 5 a – 5 c were prepared according to the published procedure [21] . Ethyl 1‐(4‐Methoxyphenyl)‐2‐(2‐methoxyphenyl)‐8,9‐dimethoxypyrrolo[2,1‐ a ]isoquinoline‐3‐carboxylate was synthesized by the known protocol [21] and used as a starting compound for the preparation of 5 d .…”

“…Compounds 5 a – 5 c were prepared according to the published procedure [21] . Ethyl 1‐(4‐Methoxyphenyl)‐2‐(2‐methoxyphenyl)‐8,9‐dimethoxypyrrolo[2,1‐ a ]isoquinoline‐3‐carboxylate was synthesized by the known protocol [21] and used as a starting compound for the preparation of 5 d . Crystallographic data for 3’ was deposited as CCDC 2244684 with Cambridge Crystallographic Data Centre.…”

Recent Advances in Biologically Active Coumarins from Marine Sources: Synthesis and Evaluation

“…For decades, many efforts have been made to develop efficient synthetic routes for these structures [ 107 ]. Within the strategies most recently described for the construction of the skeleton, we can find 1,3-dipolar cycloaddition [ 108 ], aza-Nazarov reactions [ 109 ] or Grob-type coupling [ 110 ].…”