Further investigation of the seeds of Madhuca butyracea yielded two new triterpenoid saponins, namely butyrosides C and D whose structures were established by means of chemical and spectral analyses as 3-O-beta-D-glucuronopyranosyl protobassic acid 28-O-alpha-L-rhamnopyranosyl(1-->3)-beta-D- xylopyranosyl(1-->4)-alpha-L-rhamnopyranosyl(1-->2)-alpha-L-arabinopy ranoside and 3-O-beta-D-glucuronopyranosyl 16 alpha-hydroxy protobassic acid 28-O-beta-D-apiofuranosyl(1-->3)-beta-D-xylopyranosyl(1-->4)-alpha -L- rhamnopyranosyl(1-->2)-alpha-L-arabinopyranoside, respectively.
This paper reports the asymmetric synthesis of an important pharmaceutical intermediate (3S)-1-[(1R)-2-hydroxy-1-phenylethyl]-3-methylpiperidin-2-one (compound 1) from commercially available D-plenylglycinol and delta-valerolactone. During the alkylation process, the hydroxyl group can be protected or unprotected, resulting in a different consumption of s-BuLi, and leading to a different diastereomeric excess (de) of compound 1. When 1-[(1R)-2-hydroxy-1-phenylethyl]-piperidin-2-one (compound 2) was alkylated with 2.5 eq. of s-BuLi, compound 1 was obtained as a single isomer detected by chiral high performance liquid chromatography (HPLC) columns with an overall yield of 91%. With the hydroxyl group protected, (R)-1-(2-[(tert-butyldimethylsil) oxy]-1-phenylethyl) piperidine-2-one (compound 6) could be alkylated with 1.5 eq. of s-BuLi, giving compound 1 and its diastereoisomer 8 in a ratio of 1:2.5 and a yield of methylation of 90%. Compounds 1 and 8 could be separated completely and easily by flash chromatography. The absolute configuration of compound 8 was determined by singlecrystal X-ray analysis. The mechanism of the alkylation process is discussed based on experimental results.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.