%0 Journal Article
%T A Facile Stereoselective Total Synthesis of (R)-Rugulactone
%A B. Narasimha Reddy
%A R. P. Singh
%J ISRN Organic Chemistry
%D 2014
%R 10.1155/2014/767954
%X An efficient and novel synthesis of (R)-rugulactone has been achieved employing Sharpless asymmetric epoxidation of allyl alcohols followed by selective hydride reduction of epoxy alcohols and olefin cross metathesis reactions. 1. Introduction The 6-alkyl and aryl substituted ¦Á-pyrones (6-arylalkyl-5,6-dihydro-2H-pyran-2-ones) possess important biological properties such as antitumor, antiviral, antifungal, and anti-inflammatory [1¨C12]. These properties arise as a result of Michael acceptor property of ¦Á-pyrones towards the amino acid residues of the receptors. The biological assays of 6-arylalkyl-5,6-dihydro-2H-pyran-2-one, (R)-rugulactone (1), which has been extracted from the evergreen tree Cryptocarya rugulosa [13] of Lauraceae family, have been found to inhibit the nuclear factor (NF- B) activation pathway occurring in different types of cancers [14¨C18]. Due to the attractive biological activity of (R)-rugulactone (1) (Figure 1), several total syntheses have already been reported in the literature [19¨C25]. In those reported syntheses the chiral center was created by different means: by Jacobsen¡¯s hydrolytic kinetic resolution of epoxides [19], by Keck¡¯s asymmetric allylation [21], by proline catalyzed ¦Á-aminoxylation [22] of aldehydes, by enzymatic resolution of racemic homoallylic alcohols [23], and by using a chiral pool [24, 25]. In this communication, we describe the stereoselective synthesis of (R)-rugulactone starting from inexpensive starting materials. The Sharpless asymmetric epoxidation of allyl alcohols followed by selective hydride reduction affords 1, 3-diols with high stereoselectivity. These chiral 1, 3-diols are versatile synthetic intermediates for a variety of biologically active molecules [26¨C28]. The retrosynthetic strategy of our synthesis is depicted in Scheme 1, which involves Grubb¡¯s cross metathesis between compounds 11 and 12. Scheme 1: Retrosynthesis of ( R)-rugulactone. Figure 1: ( R)-Rugulactone ( 1). 2. Materials and Methods 2.1. General Information Solvents were purified and dried by standard procedures before use. Optical rotations were measured using sodium D line on a JASCO-181 digital polarimeter. IR spectra were recorded on Thermo Scientific-Nicolet 380 FT-IR Instrument. 1H NMR and 13C NMR spectra were recorded on Brucker AC-200 spectrometer. Elemental analysis was carried out on a Carlo Erba CHNS-O analyzer. Full experimental details, 1H and 13C NMR spectra, can be found in Supplementary Material available online at http://dx.doi.org/10.1155/2014/767954. 2.2. ((3S)-3-(2-(Benzyloxy)ethyl)oxirane-2-yl)methanol, 4
%U http://www.hindawi.com/journals/isrn.organic.chemistry/2014/767954/