Synthesis of carolic acid

Hapten synthesis and development of immunoassays for methoprene

“…The reaction between 4-butyrolactone (10) and the sodium salt of benzyl alcohol gave 4-(benzyloxy)butanoic acid (Sudo et al, 1967) (Figure 2). Esterification with 2-(trimethylsilyl)ethanol, followed by catalytic hydrogenation to remove the benzyl protective group (Van Duzee and Adkins, 1935), gave 2-(trimethylsilyl)ethyl 4-hydroxybutanoate (11).…”

“…DMAP (0.734 g, 6.00 mmol) and DCC (5.92 g, 28.7 mmol) were added to a solution of 4-(benzyloxy)butanoic acid (4.44 g, 22.9 mmol), prepared according to the method of Sudo et al (1967), in dichloromethane (CH2CI2,50 mL) with stirring at 0 °C. 2-(Trimethylsilyl)ethanol (4.07 g, 34.4 mmol) in CH2C12 (50 mL) was added dropwise (Sieber et al, 1977) over a 1-h period.…”

Synthetic Strategies towards Naturally Occurring Tetronic Acids

“…49 Several years later, in an extension of Haynes' methodology, Sudo et al prepared (±)-carolic acid (160) after condensation of the ethoxymagnesium salt of ethyl e-benzyloxy-b-ketocaproate (167) with aacetoxypropionyl chloride, cyclization upon saponifica-tion, and final hydrogenolysis (Scheme 19). 50 Moreover, Svendsen and Boll replaced the intramolecular substitution step, that both Haynes and Sudo had used, with an intramolecular Michael addition (171→172), thus enabling the efficient total synthesis of (±)-carlosic (163) and (±)viridicatic acid (164) (Scheme 20). 51 A notable feature of the latter syntheses was the alkaline-induced rearrangement of the initial condensation products 172 to the final tetronic acid metabolites.…”

Addition of a Chiral Boron Enolate to Cyclic N-Acyliminium Ions. Stereocontrolled Synthesis of the Pyrrolizidine Ring System

“…Our initial attempts focused on the addition of the silyl ketene acetal and the silyl ketene thioacetal prepared from 7a and 7b , respectively, to racemic N -acyliminium ion 4 (Scheme ). As previously described for Schiff bases 5 and α-ethoxypiperidines and pyrrolidines, nucleophilic addition proceeded in the presence of trimethylsilyl trifluoromethanesulfonate (TMSOTf) to afford a 1:1 ratio of diastereoisomers 2a,b / 3a,b , in 45% and 49% yield, respectively…”