Kevin Cannon

A SECOND STUDY - PREDICTING THE 13C CHEMICAL SHIFTS FOR A SERIES OF SUBSTITUTED 3-(4-METHOXYPHENYL)-2-PHENYL-1,3- THIAZOLIDIN-4-ONES

Previously, an additivity equation relating experimental C chemical shift data for two wono-substituted diphenyl-l,3-thiazolidin-4-one series was developed to predict chemical shifts for a similarly substituted fos-disubstituted thiazolidinone series. The sites of interest in the l,3-thiazolidin-4-one are the C-2, C4, and C-5 carbons. The empirically derived equation for predicting the chemical shifts is DXY = DH + (DX-QH) + (QY-DH) where Οχγ is the predicted chemical shift for the disubstituted thiazolidinone, DH is the experimental chemical shift for the unsubstituted thiazolidinone, • χ is the experimental chemical shift for substituent in the 2-phenyl ring, and • γ is the experimental chemical shift for substituent in the N(3)-phenyl ring. This article discusses the application of the aforementioned equation with respect to a new series of substituted-2-phenyl-3-methoxyphenyl-l,3-thiazolidin4-ones, where the substituents on both phenyl rings are not the same. The equation was shown to predict a less exact chemical shift in this one test series than for the previous ft/s-disubstituted series of compounds. Introduction The genesis for our interest in the synthetic routes to l,3-thiazolidin-4-ones, and the spectroscopic properties of the products formed have been indicated extensively before. In our previous study, we reported the relationship between the experimental chemical shift values for two series of monosubstituted 2,3-diphenyll,3-thiazolidin-4-ones and a related 6w-(disubstituted)2,3-diphenyl-l,3-thiazolidin4-one series. A reasonably good correlation was obtained between experimental and predicted values for the C chemical shifts when applying Equation 1. The series of compounds used to develop the relationship of Equation 1 is shown in Figure 1. Vol. 14, No. 6, 2008 A second study predicting the C chemical shifts for A series of substituted-3Series 1: X= p-N02, m-N02,p-F, m-F,p-Cl,p-Br,m-Br, H,p-CH3, m-CH3,p-OCH}, m-OCH3; Υ = Η Series 2: Y = p-N02, m-N02, p-F, m-F, p-CI, p-Br, m-Br, H, p-CH,, m-CH3, p-OCH3, m-OCH3; χ = Η Series 3: X = Y = p-N02, m-N02, p-F, m-F, p-Cl, p-Br, m-Br, p-CH3, m-CH3, p-OCH3, m-OCH3

C1-Substituted N-tert-butoxycarbonyl-5-syn-tert-butyldimethylsilyloxymethyl-2-azabicyclo[2.1.1]hexanes as conformationally constrained β-amino acid precursors

Abstract Regioselective introduction and transformation of substituents at the C1 carbon of N-tert-butoxycarbonyl-5-syn-tert-butyldimethylsilyloxymethyl-2-azabicyclo[2.1.1]hexane (7) is described. These azabicycles are precursors to conformationally constrained β-amino acids with potential to form oligomers with definite secondary structures. Selected examples of these precursors are converted into their corresponding amino acid derivatives.

Crystal Structures of 1,3-Thiaza-4-one Heterocycles

The five-, six-, and seven-membered 1,3-thiaza-4-one heterocycles are known for their bioactivity. Five-membered 1,3-thiazolidin-4ones are known to have a very wide range of biological activity, so much that the ring system has been referred to as a “magic moiety” or “wonder nucleus” [1]. Six-membered 1,3-thiazin-4-ones have often been investigated for their biological activity and are of potential medicinal use [2]. The activity of seven-membered 1,3-thiazepan-4-ones is exemplified by the investigational compound omapatrilat [3]. Crystal structures of 1,3-thiaza-4-one heterocycles recently obtained in our laboratory will be presented.