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Discovery of Tetrasubstituted Pyrazines As Semiochemicals in a Sexually Deceptive Orchid

“…The crude product was purified by silica gel chromatography (eluent: 6% EtOAc/petroleum ether, TLC stain: bromocresol green) to give the title compound as a colorless oil (440 mg, 4 mmol, 19%). Spectroscopic data were in agreement with published data …”

“…This compound was prepared according to the procedure outlined by Tashiro and Mori. 23 (S)-2-Methylbutan-1-ol (2.45 mL, 23 mmol) was added to acetone (10 mL) at 0 °C. Freshly prepared Jones' reagent (4.47 g of Na 2 Cr 2 O 7 , in 10 mL of 25% H 2 SO 4 (aq)) was added to the stirred solution and allowed to warm to room temperature.…”

“…Spectroscopic data were in agreement with published data. 23 (S)-(3,5,6-Trimethylpyrazin-2-yl)methyl 2-Methylbutanoate (3). 2-Hydroxymethyl-3,5,6-trimethylpyrazine (1) (400 mg, 2.6 mmol) was added to a stirred solution of (S)-2-methylbutanoic acid (0.22 mL, 2 mmol) and N,N-dimethylaminopyridine (DMAP) (5 mg, cat.)…”

Total synthesis and stereochemical assignment of bipolamide A acetate

“…The known oxazolidinone 17a 8 was subjected to asymmetric ethylation 9 using Evan's protocol to access the corresponding ethylated product exclusively which was treated further with LiBH 4 to get the known alcohol 18a. 10 Notably, the adopted protocol was found to be more efficient when compared to the Evan's methylation strategy 11 where a 4 : 1 diastereoselectivity was observed. Alcohol 18a was then oxidized using TPAP/NMO followed by Wittig olefination using Ph 3 PC(CH 3 )CO 2 Et to obtain the corresponding α,β-unsaturated E-olefin exclusively which further was reacted with DIBAL-H to yield allylic alcohol 19a.…”

Total synthesis of (S)‐(+)‐ent‐phomapyrones B and surugapyrone B

“…Our synthetic route to ( S )‐(+)‐ ent‐ phomapyrone B ( ent‐ 1 ), which constitutes the construction of whole carbon skeleton of phomapyrone B via the condensation of the acid chloride 5 with malonic acid mono‐ethyl ester followed Claisen condensation starting from the chiral alcohol 3 and subsequent cyclization into 2‐pyrone, is summarized in Scheme . The commercially‐available ( S )‐2‐methyl‐1‐butanol ( 3 ) was oxidized with Jones' reagent to afford the carboxylic acid 4 in 74% yield . Conversion of 4 into the acid chloride 5 followed by condensation with malonic acid mono‐ethyl ester 6 in the presence of n ‐butyl lithium provided the chiral β ‐keto ester 7 in 68% yield .…”