Total Syntheses of Graphisin A and Sydowinin B

Abstract

Efficient syntheses of the highly substituted benzophenone graphisin A and the xanthone sydowinin B are described. Key steps involve aryl anion addition to substituted benzaldehyde derivatives, subsequent methyl ester installation, and dehydrative cyclization. Oxidation of graphisin A led to a spirodienone derived from a highly substituted benzoquinone intermediate.

Cytotoxic Polyketides from the Deep-Sea-Derived Fungus Engyodontium album DFFSCS021

“…Engyodontiumone A ( 1 ) had a molecular formula of C 17 H 14 O 7 as established by HRESIMS ( m/z 331.0801 [M + H] + ). Its NMR data ( Table 1 and Table 2 ) was similar to that of sydowinin B [ 5 , 6 ] with the only difference of one methoxyl (δ C 56.8) and the absence of a hydroxyl proton signal in 1 , which indicated that 1 was a chromone skeleton. In the HMBC spectrum (see Supporting Information Figure S3 ), correlations of δ H 12.11 with C-7/C-8/C-13 suggested a hydroxyl group located at C-8, correlations of δ H 3.88 (3H, s) with C-2 suggested a methoxy group located at C-2, and correlations of δ H 4.60 (2H, s) with C-5/C-6/C-7 suggested a hydroxymethene group attached at C-6.…”

“…Engyodontiumone B ( 2 ) had a molecular formula of C 16 H 11 ClO 6 as inferred from its HRESIMS ( m/z 335.0309 [M + H] + ) showing peaks at m/z 335.0309 and 337.0264 with the height ratio of 3:1. Its NMR data ( Table 1 and Table 2 ) showed great similarity to those of sydowinin B [ 5 , 6 ] with the only obvious difference of the high-field shift of the chemical shift of C-2 (from δ C 148.9 in sydowinin B to δ C 125.5 in 2 ) suggesting the loss of the hydroxyl functionality. Combined with the molecular formula and HMBC spectral data (see Supporting Information Figure S8 ), these data suggested a chlorine atom attached at C-2.…”

“…Preliminary experiments demonstrated that the extract of the culture medium of the strain showed toxicity towards brine shrimp and antibacterial activity. Further investigation on the chemical constituents of the extract resulted in the isolation of eight new chromones ( 1 – 8 ) and three new phenol derivatives ( 9 – 11 ) together with eight known compounds: sydowinin A ( 12 ) [ 4 ], pinselin ( 13 ) [ 5 ], sydowinin B ( 14 ) [ 5 , 6 ], aspergillusone B ( 15 ) [ 7 ], AGI-B4 ( 16 ) [ 8 ], diorcinol ( 17 ) [ 9 ], cordyol C ( 18 ) [ 10 ], and hydroxysydonic acid ( 19 ) [ 11 ] ( Figure 1 ). The cytotoxicity, antibacterial, and antilarval activities of these compounds were individually evaluated.…”

Asymmetric Total Syntheses and Structure Revisions of Eurotiumide A and Eurotiumide B, and Their Evaluation as Natural Fluorescent Probes

“…We initially prepared the aldehyde derivative and PT‐sulfone as substrates of the Julia–Kocienski olefination (Scheme ). Aldehyde 12 was synthesized by a sequential operation of bromination of commercially available 2,5‐dihydroxybenzaldehyde ( 10 ) and MOM protection of the two phenolic hydroxyl groups ( 11 ) (Scheme a). PT‐sulfone 9 was obtained through the Mitsunobu reaction of 1‐phenyl‐1 H ‐tetrazol‐5‐yl thiol (PT‐SH) with n ‐hexanol ( 13 ) followed by oxidation of the sulfide to sulfone (Scheme b).…”

Asymmetric Total Syntheses and Structure Elucidations of (+)-Eurotiumide F and (+)-Eurotiumide G

“…which could be prepared in decagram scale and good enantiomeric purity in 4 steps from aldehyde 9 21,22) and 1-phenyl-1Htetrazol-5-yl (PT)-sulfone 10, by Julia-Kocienski olefination, asymmetric Shi epoxidation, 23) BF 3 -OEt 2 mediated epoxide opening, and Pd-catalyzed C1 insertion/lactonization cascade reaction [24][25][26][27] (Chart 2). The propargyl moiety was introduced by the treatment of 8 with 3-chloro-3-methylbut-1-yne in the presence of 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) and catalytic amount of CuCl 2 to afford propargyl derivative 7 in good yield.…”