Well-defined AB 3 -type miktoarm star-shaped polymers with cholic acid (CA) core were fabricated with a combination of "click" chemistry and ring opening polymerization (ROP) methods. Firstly, azide end-functional poly(ethylene glycol) (mPEG), poly(methyl methacrylate) (PMMA), polystyrene (PS), and poly(e-caprolactone) (PCL) polymers were prepared via controlled polymerization and chemical modification methods. Then, CA moieties containing three OH groups were introduced to these polymers as the end groups via Cu(I)-catalyzed click reaction between azide end-functional groups of the polymers (mPEG-N 3 , PMMA-N 3 , PS-N 3 , and PCL-N 3 ) and ethynylfunctional CA under ambient conditions, yielding CA endfunctional polymers (mPEG-Cholic, PMMA-Cholic, PS-Cholic, and PCL-Cholic). Finally, the obtained CA end-capped polymers were employed as the macroinitiators in the ROP of e-caprolactone (e-CL) yielding AB 3 -type miktoarm star polymers (mPEG-Cholic-PCL 3 , PMMA-Cholic-PCL 3 , and PS-Cholic-PCL 3 ) and asymmetric star polymer [Cholic-(PCL) 4 ]. The chemical structures of the obtained intermediates and polymers were confirmed via Fourier transform infrared and 1 H nuclear magnetic resonance spectroscopic techniques. Thermal decomposition behaviors and phase transitions were studied in detail using thermogravimetric analysis and differential scanning calorimetry experiments.

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An efficient stereospecific synthesis of the plant hormone ( RS)-abscisic acid from the readily available 4-oxoisophorone, trimethylsilylacetylene and ethyl but-2-ynoate, is described.

A novel hexa-armed and star-shaped polymer containing cholesterol end-capped poly(e-caprolactone) arms emanating from a phosphazene core (N 3 P 3 -(PCL-Chol) 6 ) was synthesized by a combination of ring-opening polymerization and "click" chemistry techniques. For this purpose, the terminal AOH groups of the synthesized precursor (N 3 P 3 -(PCL-OH) 6 ) were converted into -Chol through a series of reaction. Both N 3 P 3 -(PCL-OH) 6 and N 3 P 3 -(PCL-Chol) 6 were then employed in the preparation of supramolecular inclusion complexes (ICs) with b-cyclodextrin (b-CD). The latter formed ICs with b-CD in higher yield. The host-guest stoichiometry (e-CL:b-CD, mol:mol) in the ICs of N 3 P 3 -(PCL-Chol) 6 was found to be 1.2. The formation of supramolecular ICs of N 3 P 3 -(PCL-Chol) 6 with b-CD was confirmed by using Fourier transform infrared (FTIR) and 1 H nuclear magnetic resonance (NMR) spectroscopic methods, wide-angle X-ray diffraction (WAXD), and thermal analysis techniques. WAXD data showed that the obtained ICs with N 3 P 3 -(PCL-Chol) 6 had a channel-type crystalline structure, indicating the suppression of the original crystallization of N 3 P 3 -(PCL-Chol) 6 in b-CD cavities. Moreover, the thermal stabilities of ICs were found to be higher than those of the free star polymer and b-CD. Furthermore, the surface properties of N 3 P 3 -(PCL-Chol) 6 and its ICs with b-CD were investigated by static contact angle measurements. The obtained results proved that the wettability of N 3 P 3 -(PCL-Chol) 6 successfully increased with the formation of its ICs with b-CD. V C 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3406-3420

A comparison between the -and -facial selectivity observed in the hydroboration of some androst-5-enes and B-norandrost-5-enes does not parallel the difference between the calculated force field energies for -and -cyclobutane models suggesting that the facial selectivity is not determined by the four-centre transition state but by the relative ease of formation of the initial %-complex between the alkene and the borane.