136749-43-4Relevant articles and documents
A non-enzymatic synthesis of (S)-(-)-rosmarinic acid and a study of a biomimetic route to (+)-rabdosiin
Bogucki, David E.,Charlton, James L.
, p. 1783 - 1794 (1997)
The synthesis of (S)-(-)-rosmarinic acid (30) in 9% overall yield is described. The synthesis was achieved by a convergent route in which 3-(3′,4′-dihydroxyphenyl)-(S)-lactic acid (23) and caffeic acid (25), both appropriately protected, were coupled to produce a pentaallyl precursor 29, which was then deprotected to give (S)-(-)-rosmarinic acid (30). A triallyl derivative 35 was similarly prepared and converted to (+)-rabdosiin (41) and its (1R,2S) isomer (42) via a biomimetic oxidative free radical coupling-cyclization followed by deallylation. The coupling-cyclization gave a ratio of rabdosiin diastereomers unlike that found in nature. A preliminary study showed that methyl (R)-mandelyl sinapate (15) could be dimerized diastereoselectively to give a 1,2-trans thomasidioate diester (16). The synthesis of (S)-(-)-rosmarinic aid (30) in 9% overall yield is described. The synthesis was achieved by a convergent route in which 3- (3',4'-dihydroxyphenyl)-(S)-lactic acid (23) and caffeic acid (25), both appropriately protected, were coupled to produce a pentaallyl precursor 29, which was then deprotected to give (S)-(-)-rosmarinic acid (30). A triallyl derivative 35 was similarly prepared and converted to (+)-rabdosiin (41) and its (1R,2S) isomer (42) via a biomimetic oxidative free radical coupling- cyclization followed by deallylation. The coupling-cyclization gave a ratio of rabdosiin diastereomers unlike that found in nature. A preliminary study showed that methyl (R)-mandelyl sinapate (15) could be dimerized diastereoselectively to give a 1,2-trans thomasidioate diester (16).
Chiral 2-Benzopyran-3-carboxylates by Oxa-Pictet-Spengler Reaction of (S)-3-Phenyllactic Acid Derivatives
Wuensch, Bernhard,Zott, Matthias
, p. 39 - 46 (2007/10/02)
Starting with (S)-tyrosine, the methyl (S)-3-(3,4-dihydroxyphenyl)lactate (15b) was prepared by acylation, desamination and Dakin oxidation.The phenyl moiety of 15b was sufficiently activated for the reaction with aromatic and aliphatic aldehydes and ketones to yield the alkyl (3S)-2-benzopyran-3-carboxylates 16 and 19.On the other hand, the oxa-Pictet-Spengler reaction of the aryl unsubstituted (S)-3-phenyllactic acid (6) succeeds only with aromatic aldehydes.It was shown that the enantiomeric purity of the compounds 13, 14, 15, 16 and 19 was greater than 96percent ee. Key Words: Oxa-Pictet-Spengler reaction / (S)-3-Phenyllactates / (3S)-2-Benzopyran-3-carboxylates