B.B. Shankar

One pot solid phase synthesis of isoxazolines

Abstract 1,3 Dipolar cycloadditions of nitrile oxides generated in situ on solid phase in the presence of a variety of dipolaraphiles provided a library of isoxazolines and isoxazoles.

Synthesis of an optically pure 3-unsubstituted β-lactam using an asymmetric Reformatsky reaction and its conversion to cholesterol absorption inhibitors

Abstract Asymmetric induction by several chiral alcohols in the reaction of their bromoaceates with imines in the presence of activated Zn (Reformatsky reaction) was studied. Trans -2-phenylcyclohexanol and phenyl menthol gave β-lactam 9 , obtained by cyclizing the diastereoisomeric β-aminoesters 8 , in > 99%ee. The resulting chiral 3-unsubstituted azetidin-2-one 9 was converted to 3-substituted products 11, 12 , and 13 which exhibit cholesterol absorption inhibitory activity.

A new ring synthesis for 3- and polysubstituted furans; directing effects of a 3-(arenesulfonyl) group in metalation and Friedel-Crafts processes

Abstract Primary and secondary α-bromoketones react with the potassium salt (3) to afford 2-[E-2-(p-toluenesulfonyl)-ethenyloxy]-ketones. On treatment with LDA followed by p-TsOH, good yields of the corresponding 3- or 2,3-substituted-4-tosylfuran are obtained, from which the 4-substituent may be reductively removed. 3-Aryl or alkyl-4-tosylfurans undergo regiospecific metalation at C-5 and Friedel-Crafts acylation at C-2. These processes permit the conversion of bromoketones to 2,3-, 2,4- or 2,3,5-substituted furans.

A concise route to the oxathiazepine containing eudistomin skeleton and some carba-analogs

Abstract The unsubstituted Eudistomin skeleton containing the oxathiazepine D ring was prepared along with a series of unsubstituted and amino-substituted carba-analogs, using an intramolecular Pictet-Spengler condensation.

Configurational properties and chemical reactivity of mono and dianions derived from aryl 2-alkoxyvinyl sulfones

Abstract E-2-Alkoxy-1-arylsulfonylethenes are regio and stereospecifically lithiated at C-1 and the resulting species react efficiently with a variety of electrophiles to give synthetically useful products.

Indolocarbazoles. 2. Synthetic studies towards staurosporine. An unexpected 1,2 migration of indolocarbazole nitrogen results in a novel and potent Protein kinase C inhibitor.

Abstract Attempted transformation of the readily accessible cyclofuransylated indolocarbazole (4) to a cyclopyranosylated compound related to 1 was explored. An unexpected rearranged product (10) was obtained from (9). Compound (10) was converted to (14), a potent PKC inhibitor. The mechanism of the rearrangement was unraveled with a deuterium labeling experiment.

A novel application of “benzotriazole” methodology : Reactions of polyhydroxylated bis-(benzotriazolyl) piperidines with mono- and bidentate nucleophiles.

Abstract A variety of 2,6 substituted trihydroxy piperidines 4 was synthesized with stereocontrol from the corresponding 2,6 bis-(Benzotriazolyl) trihydroxy piperidine 9 , which in turn was prepared from 1,2-O-isopropylidene-D-glucofuranose 5 employing a simple, two step chemical manipulation. These products are potential glycosidase inhibitors and can be transformed to other useful chiral products.

Indolocarbazoles.3. Synthesis of novel aza analogs of staurosporine and K 252a as PKC inhibitors.

Abstract Indolocarbazole 4 and arcyriaflavin A 19 reacted under basic conditions with 1-benzyl-2,6-bis (benzotriazolyl)-piperidine to give 5 and 20 . As an extension of this methodology other related bis benzotriazole derivatives were synthesized and coupled with 19 to obtain a variety of aza derivatives 3 . N-dbenzylation of these compounds gave novel PKC inhibitors.