Three conjugates based on dendrimer PAMAM generation five were synthesized and radiolabeled successfully. To investigate their tumor targeting, the in vitro and in vivo stability, cell uptake, in vivo biodistribution, and micro-SPECT imaging were evaluated, respectively. The conjugate of (99m)Tc labeled PEGylated dendrimer PAMAM folic acid conjugate ((99m)Tc-G5-Ac-pegFA-DTPA) shows much higher uptake in KB cancer cells and accumulated more in the tumor area than that of the other two conjugates. The uptake in KB cells depends on the incubation time. The results of in vivo biodistribution agree with the data obtained from micro-SPECT imaging. These studies show that PEGylation of PAMAM dendrimer folic acid conjugate improves the tumor targeting. Folate-conjugated dendrimer maybe developed to be potential radiopharmaceuticals and targeted drug delivery systems.

The side chain of a compound plays an important role in its biological function. In our studies, we have found that hydroximinosteroid derivatives with different side chains and position of hydroximino on ring A and B displayed remarkable distinct cytotoxicities against a diversity of cancer cell types. Presence of an oxime group on ring B and a hydroxy on ring A or B resulted in a higher cytotoxicity than other structural motifs. In addition, a cholesterol-type side chain at position 17 was required for the biological activity. Our findings provide new evidence showing the relationship between the chemical structure and biological function. The information obtained from the studies may be useful for the design of novel chemotherapeutic drugs.

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Using beta-sitosterol as a starting material, (6E)-hydroximino-24-ethylcholest-4-en-3-one (1), a natural steroidal oxime from Cinachyrella alloclada and C. apion, was synthesized in four steps with a high overall yield. First, beta-sitosterol (5a) is transformed into the corresponding 24-ethylcholest-4-en-3,6-dione (6a) via oxidation with pyridinium chlorochromate (PCC). Selective reduction of 6a by NaBH(4) in the presence of CoCl(2) gives 24-ethylcholest- 4-en-3beta-ol-6-one (7a). The reaction of 7a with hydroxylamine hydrochloride offers the oxime 8a and the oxidation of 8a by Jones reagent gives the target steroid 1. (6E)-Hydroximinocholest-4-en-3-one (2) and (6E)-hydroximino-24-ethylcholest-4,22-dien-3-one (4) were synthesized by a similar method. The cytotoxicity of the synthesized compounds against sk-Hep-1 (human liver carcinoma cell line), H-292 (human lung carcinoma cell line), PC-3 (human prostate carcinoma cell line) and Hey-1B (human ovarian carcinoma cell line) cells were investigated. The presence of a cholesterol-type side chain appears to be necessary for the biological activity.

A novel strategy for the direct carboxyl transfer involving a decarboxylative A 3 reaction of α-keto acids, primary amines, and alkynes has been developed under a Cu(I)/Cu(II) binary catalysis system. This multicomponent reaction provides a facile and efficient approach for the production of a diverse range of 2oxazolidinones in moderate to excellent yields through a one-pot CO 2 elimination−fixation procedure. The conciseness of the "CO 2 recycling" process makes this ideal synthesis superior over classical CO 2 utilization.

Herein we describe a highly chemoselective A 3 -coupling/annulation of amino alcohols, formaldehyde, two kinds of aldehydes and alkynes, catalyzed by copper(II). This cascade reaction, employing readily available materials, provides a new and highly effective access to chiral N-propargyl oxazolidines with good diastereoselectivity (up to >20:1). In the case of orthosubstituted aromatic aldehydes, an intriguing steric effect is observed: a bulky group exhibits a remarkably adverse effect on the diastereoselectivity for the formation of the title molecule.

A microwave‐assisted copper‐catalyzed A3 cross‐coupling/decarboxylative A3 domino reaction of a propiolic acid, an aldehyde, a formaldehyde solution and an amine is described. This strategy represents the first one‐pot cross‐coupling reaction for the direct synthesis of trisubstituted unsymmetrical 2‐butynes with a broad functional group tolerance in good yields (up to 91 %) and excellent chemoselectivity. The simultaneous activation of both the C−COOH and C−H bond of propiolic acid is crucial in this approach, and only carbon dioxide and water are generated as byproducts.

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