Carl R. Johnson

Direct α-iodination of cycloalkenones

Abstract The direct preparation of α-iodoenones by treatment of enones with I 2 /pyridine in CCl 4 is described.

Trimethylsilyl chloride/tetramethylethylenediamine facilitated additions of organocopper reagents (RCu) to enones

Abstract Alkylcoppers (RCu) add readily in a conjugate fashion to enones in the presence of TMSCl and TMEDA to give high yields of trimethylsilyl enol ethers.

Modified stille coupling utilizing α-iodoenones

Abstract α-Iodoenones undergo Pd-catalyzed coupling with alkenyl- and aryl-tributylstannanes providing an efficient route to the corresponding α-substituted enones.

Enzymatic asymmetrization of meso-2-cycloalken--1,4-diols and their diacetates in organic and aqueous media

Abstract meso -2-Cycloalken-1,4-diols or the corresponding diacetates with five-, six-, and seven-membered rings were subjected to enzymatic asymmetrizations utilizing a recombinant version of lipase B from Candida antarctica (Novo SP-435) in organic or aqueous media.

N,S-dimethyl-s-phenylsulfoximine: A reagent for the optical resolution of ketones

Abstract The addition of the α-lithio derivative of (+)- or (-)-N,S-dimethyl-S-phenylsulfoximine to selected dl -ketones was carried out at -78° in tetrahydrofuran followed by acid quench at that temperature to produce mixtures of diastereomeric β-hydroxysulfoximines. The optically-active diastereomers were chromatographically separated on sil recycled.

Synthesis of the carbocyclic nucleoside (-)-neplanocin A

Abstract (−) - Neplanocin A has been prepared in 14 steps from cyclopentadiene (11% overall yield).

Synthesis of (+)-1-deoxygalactonojirimycin and a related indolizidine

Abstract Amido-alcohol 1 is transformed via aminal 2 into 1-deoxygalactonojirimycin ( 3 ) and the structurally related indolizidine 4 .

Scaffolded bis-azasugars: A dual warhead approach to glycosidase inhibition

Abstract Double Suzuki coupling was achieved with vinyl bromide 7 , synthesized from the bromobenzene microbial oxidation metabolite bromocyclohexadienediol 6 and α,ω-diborane coupling partners derived from the hydroboration of the corresponding diene. Ozonolysis and selective reduction protocols served to provide selectively theα/α or β/β tethered polyhydroxylated piperidine ring systems (bis-azabugars). The C 8 linked DMJ analogue 1 showed inhibitory activity against glycosidase enzymes.

Synthesis of aza-C-disaccharides - a new class of sugar mimics

Abstract Synthesis of a novel aza- C -disaccharide is described using a Suzuki coupling of the alkyl boron reagent 8 and vinyl bromide 7 as the key step.

Enantioselective synthesis of 6-cycloheptene-1,3,5-triol derivatives by enzymatic asymmetrization

Abstract Starting from cycloheptatriene, 3,5-cycloheptadienol ( 1 ) has been prepared and elaborated to meso -6-( t -butyldimethylsilyloxy)-2-cycloheptene-1,4-diols ( 3 and 6 ). Enzymatic asymmetrization of these diols with Pseudomonas cepacia lipase in isopropenyl acetate provides optically pure skipped triol derivatives 4a and 7a .