• Bulletin of the Korean Chemical Society
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• v.35 no.12
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• pp.3627-3631
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• 2014

In this study we examined two ester-containing cross-links, hex-2-enyl acetate and hex-2-enyl propionate, as new cross-linking systems for helix stabilization of short peptides. We demonstrated that these hexenyl ester cross-links can be readily installed via a ruthenium-mediated ring-closing metathesis reaction of L-aspartic acid 4-allyl ester or L-glutamic acid 5-allyl ester at position i and (S)-2-(4'-pentenyl)alanine at position i+4 using second generation Hoveyda-Grubbs catalyst at $60^{\circ}C$. Between these two cross-links, we found that the hex-2-enyl propionate significantly stabilizes the ${\alpha}$-helical conformations of short model peptides. The helix-stabilizing effects of the hex-2-enyl propionate tether appear to be as powerful as Verdine's i,i+4 all-hydrocarbon stapling system, which is one of the most widely used and the most potent helix-stabilizing cross-linking systems. Furthermore, the hex-2-enyl propionate bridge is reasonably robust against non-enzymatic hydrolytic cleavage at a physiological pH. While extended studies for probing its chemical scopes and biological applications are needed, we believe that this new helix-stabilizing system could serve as a useful chemical tool for understanding protein folding and designing conformationally-constrained peptide drugs.

• Korean Journal of Food Science and Technology
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• v.30 no.3
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• pp.638-643
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• 1998

The volatile flavor components in Takju made from mashed glutinous rice and barley rice were identified by GC and GC-MS using polar column. Twenty eight kinds of flavor compounds including 10 alcohols, 9 esters, 2 acids, 7 aldehydes were identified. At the beginning of fermentation 14 kinds of volatile components were detected and the kinds of volatile components were increased up to maximum after fermentation for 16 days. The contents of volatile components in the sample made from glutinous rice contained slightly higher than the sample made from barley rice. Ethyl alcohol, n-propyl alcohol, iso-amyl alcohol, n-hexyl alcohol, hexenyl alcohol, 2-phenylethyl alcohol, ethyl acetate, ethyl succinate, 2-phenylethyl acetate, butyic acid, benzaldehyde and 3-methoxybenzaldehyde were detected in the both of the sample throughout the fermentation process. Five kinds of aldehyde including ethyl propionate, iso-amyl acetate, ethyl caprylate and ethylphenyl acetate were detected only in the sample fermented for 16 days. The main components of the both sample were ethyl alcohol, iso-amyl alcohol, 2-phenylethyl alcohol, 2-phenylethyl acetate, hexenyl alcohol and iso-butyl alcohol. Besides ethyl acetate and benzaldehyde from glutinous rice Takju and hexenyl alcohol from barley rice Takju were found as main components.