Determination of lead by the precipitation of lead molybdate from a homogeneous solution by the diffusion method

A satisfactory quantitative method for the determination of lead as lead molybdate by precipitation from a homogeneous solution has been developed. The method employs the diffusion of ammonia into a solution containing lead and sodium molybdate in nitric acid medium. The precipitation of lead in the range of 28·0–280·0 mg is complete within 8–9 hours. Anions like sulphate, arsenate, phosphate, tungstate and chromate in moderate concentrations and cations such as Zn (II), Cu (II), Ni (II), Co (II), Mn (II), Cd (II), Hg (II), Ag (I), Ti (IV), As (V), Mg (II) and Al (III) do not contaminate the precipitate. The precipitate gets constant weight at 120°. This eliminated the ignition of the precipitate,i.e., the contamination of molybdic oxide by the precipitate was reduced.     

The Stereoselective Total Synthesis of (6S)‐5,6‐Dihydro‐6‐[(2R)‐2‐hydroxy‐6‐phenylhexyl]‐2H‐pyran‐2‐one via Prins Cyclization

The stereoselective total synthesis of an antiproliferative and antifungal α‐pyrone natural product (6S)‐5,6‐dihydro‐6‐[(2R)‐2‐hydroxy‐6‐phenylhexyl]‐2H‐pyran‐2‐one is described. The key steps involved are the Prins cyclization, Mitsunobu reaction, and ring‐closing metathesis reaction.     

Total Synthesis of Aculeatins A and B from L‐Malic Acid

An efficient total synthesis of the cytotoxic spiroketal natural products aculeatin A and B is described. The synthesis of the 1,3,5‐triol moiety with appropriate configuration was accomplished from the commercially available L ‐malic acid. The key steps in this synthesis are the Barbier allylation, LiAlH₄/LiI‐mediated syn‐stereoselective 1,3‐asymmetric reduction, and phenyliodine bis(trifluoroacetate) (=[bis(trifluoroacetoxy)iodo]benzene; PIFA) mediated oxidative spirocyclization.     

Stereoselective Synthesis of the C(1) – C(28) Fragment of Amphidinol 3

A stereoselective synthesis of the polyol side chain (C(1) – C(28)) of amphidinol 3 has been accomplished following Sharpless epoxidation, Crimmins aldol reaction, Jacobsen kinetic resolution, Sharpless asymmetric dihydroxylation, and our own reaction for the synthesis of a chiral allylic alcohol from an epoxy alcohol. The olefin functionality was introduced by a cross metathesis and Julia–Kocienski olefination.     

Determination of cadmium by precipitation of cadmium molybdate from homogeneous solution

A quantitative method has been developed for the determination of cadmium as cadmium molybdate by PFHS method using the technique of volatalisation of ammonia. The pH range for complete precipitation is found to be 6·0–7·6. Presence of 20–50 mmoles acetate is necessary for obtaining quantitative results. From 20–200 mg of cadmium could be conveniently determined using this method. Zinc, magnesium and nickel do not interfere. The anions such as sulphate, acetate, nitrate and chloride can be tolerated up to 50 mmoles. The precipitate has constant weight upto 750°.