Proton-transfer steps in Steglich esterification: a very practical new method for macrolactonization

Abstract

where F is the fraction of reaction (0.51-0.79 in the present experiments), R is the molar activity of recovered, and R0 is the molar activity of the original reactant.

A convenient synthesis of long-chain 4-substituted benzyloxycarbonyl alkanethiols for the formation of self assembled monolayers on metal substrates

“…The best reaction conditions were those given in Entry 3 using 0.5 equivalent of DMAP and 1.1 equivalents of DCC per equivalent of 1 and they were consequently enforced to all other esterification reactions. The reaction runs smoothly if the reagent DCC is added slowly to the reaction mixture of 1, 2 and DMAP (see experimental), which has also been recommended by others [19].…”

“…Commercially available 16-bromohexadecanoic acid 1 was allowed to react with 4-substituted benzyl alcohols 2a-d in dry diethyl ether using the DCC/DMAP (4-dimethylaminopyridine) reaction conditions [19,20,21]. It was necessary to carefully optimize the reaction conditions, since formation of substantial amounts of the byproduct 4 was observed.…”

Synthesis of Cholic Acid-Peptide Conjugates With A Negatively Charged Ester Linkage for Oral Delivery

“…Three other hydroxyl groups on the steroid ring of cholic acid at C3, C7, and C12 also have the potential of forming ester bonds with peptide unit resulting in an unwanted mixture of different peptide esters. To avoid side reactions and to increase the regio-selectivity of esterification, ethyl acetate was used as the solvent for DCC esterification reaction in the presence of a small amount of 4-dimethylaminopyridine (DMP) (5%) or triethylamine (TEA) (10%) as catalyst [20,21]. Among several solvents examined in our experiments, ethyl acetate was found to be the most suitable because of the higher selectivity and higher yield than other solvents including dichloromethane, tetrahydrofuran and acetonitrile.…”

Determination of the Absolute Stereostructure of seco-Macrosphelide E Produced by a Fungal Strain from a Sea Hare.

“…4) The key compound in the synthesis of (ϩ)-1 and (ϩ)-3 is (4R,5S)-4-benzyloxy-5-silyloxy-2(E)-hexenoic acid 7 and this compound was also used for the synthesis of 2 or 4 as a starting material. Condensation of carboxylic acid (4R,5S)-7 and commercially available (3R)-hydroxy butanoate 8 via the Keck procedure 5) MS) of (3R,8R,9S,14R,15S))-2 and (3S,8R,9S,14R,15S)-4 quite resembled those of the natural product 2, respectively, while both retention times of (3R,8R,9S,14R,15S)-2 (t R ϭ19.3 min) and (3S,8R,9S,14R, 15S)-4 (t R ϭ25.8 min) by mean of HPLC (column; CHIRAL-CEL OD (0.46ϫ25 cm), solvent; n-hexane-EtOH (10 : 1); detection; 254 nm) were quite different. The retention time of (3R,8R,9S,14R,15S)-2 was found to be consistent with that (t R ϭ19.3 min) of the natural product 2.…”