Total Syntheses of the Marine Pyrrole Alkaloids Polycitone A and B

Abstract

Polycitone B (2) was obtained in four steps from pyrrole dicarboxylic acid 3, including Friedel-Crafts reaction of the corresponding acid chloride with anisole. The conversion of 2 into polycitone A (1) was achieved in two steps via Mitsunobu alkylation of the pyrrolic NH group. The synthesis of polycitone A proceeds in 18% overall yield and offers the possibility of varying the substituents on the pyrrole ring.

An efficient stereoselective total synthesis of 11β-methoxycurvularin

“…The resulting mixture was then allowed to settle for 1 h before filtration through Celite using Et 2 O and then concentrated under reduced pressure. The residue was purified on silica gel column chromatography using (EtOAc/hexanes, 3:7) as eluent to afford compound 11 as colourless oil (1.63 g, 70 % (17). To freshly distilled ammonia (25 mL) in a 100 mL two neck round bottom flask fitted with a cold finger condenser, was added catalytic amount of ferric nitrite, followed by the piecewise addition of lithium metal (166 mg, 18.5 mmol) at -33 o C. The resulting grey color suspension was stirred for 30 min.…”

“…Intramolecular Friedel-Crafts acylation of 6 was achieved using a mixture of trifluoroacetic acid and trifluoroacetic anhydride [17][18][19][20] to give a macrolide 20 in 50% yield. Finally, the deprotection of 20 with freshly prepared AlI 3 in benzene gave the target molecule, 11β-methoxycurvularin 5 in 65% yield as colorless oil.…”

Selective Mono-reduction of Pyrrole-2,5 and 2,4-Dicarboxylates

“…Much attention has been focused on highly substituted pyrroles including 3,4-diaryl groups found in a class of alkaloids [1][2][3][4][5][6][7][8][9][10][11][12] ( Fig. 1).…”

“…1). We previously reported a synthetic reaction of 3,4-diarylpyrrole-2,5-dicarboxylates from α-diazoesters through a [3,3]-sigmatropic rearrangement of azine, which was also applied to the formal syntheses of polycitones (1) and permethyl storniamide (3b) 13,14) (Chart 1). This reaction is a very concise method but is not directly applicable to the preparation of unsymmetric pyrrole found in Ningalin B (4b) 8) and lamellarins (5).…”

Application of aluminum triiodide in organic synthesis

“…Surprisingly, the allylic group para to phenolic hydroxyl group was reduced to propyl group when eugenol (97) was demethylated under the condition, and furnished 98 in 81% yield. 76 Polycitone B (104, see Scheme 8B), 77 biaryl plural neolignan honokiol and magnolol (107, see scheme 8C), 78 and non-steroidal Estrogen receptor antagonists R1128 A~D (109, see Scheme 8D) 79 were accomplished similarly in moderate to high yields. It is noteworthy that deprotection of 108 with BBr 3 resulted in partially demethylated mixtures; besides, the 9,10-anthraquinone skeleton was not affected by AlI 3 .…”