Norman J. Lewis

Regiospecific Reduction of 5-Benzylidene-2,4-Thiazolidinediones and 4-Oxo-2-thiazolidinethiones using Lithium Borohydride in Pyridine and Tetrahydrofuran

Abstract The novel regiospecific and general reduction of 5-benzylidene-2,4-thiazolidinediones and 5-benzylidene-4-oxo-2-thiazolidinethiones to the corresponding 5-benzyl derivatives has been accomplished using lithium borohydride in pyridine and tetrahydrofuran. Sodium borohydride and lithium chloride can also be used under these conditions, which represents a cheaper alternative to lithium borohydride.

ASYMMETRIC SYNTHESIS OF THE MC7N CORE OF THE MANUMYCIN FAMILY : PREPARATION OF (+)-MT 35214 AND A FORMAL TOTAL SYNTHESIS OF (-)-ALISAMYCIN

An asymmetric approach to the mC7N epoxyquinone central unit of the manumycin antibiotics is described based on the enantioselective (89% ee) chiral phase transfer epoxidation of a substituted cyclohexenone. The chiral epoxide is employed in the first syntheses of the title compounds in enantiomerically pure form.

Synthetic approaches to the Manumycin A, B and C antibiotics: The first total synthesis of (+)-Manumycin A

Abstract The first total synthesis of Manumycin A, as its (+)-enantiomer, is reported. The synthetic route features an asymmetric epoxidation (based on Wynbergs chiral phase transfer methodology) for the preparation of the key epoxyquinol nucleus, and a further demonstration of the utility of the Stille reaction for the construction of the Manumycin lower side chain. This synthesis of Manumycin A corrects the original stereochemical assignment and confirms the syn -hydroxy epoxide arrangement. The first syntheses of the quinones obtained by the oxidative degradation of Manumycins A-C are also described.

N-tert-Butoxycarbonyl (BOC) Deprotection Using Boron Trifluoride Etherate

Abstract A mild and efficient procedure is described for the removal of the tert-butoxycarbonyl (BOC) group using boron trifluoride etherate and molecular sieves in dichloromethane at room temperature. The scope of this procedure is explored for the deprotection of a variety of amines including amino acid derivatives.

Synthesis of bromoxone

Abstract A short synthetic route to the natural product bromoxone is reported (5 steps, 15% overall yield), involving regioselective monoepoxidation of an electrolytically-derived quinone monoketal followed by stereoselective ketone reduction.

Unsaturated amides derived from 2-amino-3-hydroxycyclopentenone: A stille approach to the synthesis of asuka-mABA, 2880-II, and limocrocin

Abstract A Stille palladium catalysed vinyl halide-vinyl stannane or aryl stannane coupling approach to the title compounds is described. The 2-aminocyclopentanedione-derived vinyl bromides ( 12 , n = 1,2,3) were prepared and coupled to synthesise 2880-II ( 4 ), a Streptomyces metabolite, asuka- m ABA ( 6 ), obtained during investigations to elucidate the biogenesis of the antibiotic asukamycin, and limocrocin ( 10 ), a naturally occurring antibiotic and antiviral agent.

The synthesis of novel analogues of the manumycin family of antibiotics and the antitumour antibiotic LL-C10037α

Abstract Efficient approaches to the central amino-epoxycyclohexenone core of the manumycin family of antibiotics are described. The use of this methodology to prepare the antitumour antibiotic LL-C10037α and its epimer, both in racemic form, and a number of analogues of manumycin, alisamycin and asukamycin, lacking the C-4 substituent, are then outlined.

The total synthesis of the diepoxycyclohexanone antibiotic aranorosin and novel synthetic analogues

A short synthesis of the novel antibiotic aranorosin in chiral form is described which employs (i) a novel hypervalent iodine-mediated oxidative hydroxylation of a tyrosinal derivative and (ii) a stereocontrolled cis-bisepoxidation in the key steps. A similar procedure was employed to prepare 6′-epiaranorosin, and hence establish the stereochemistry of the natural compound, and to prepare novel aranorosin analogues. An organometallic route is described which gives desamidoaranorosin.

An Efficient, Simple and Inexpensive Method for the Preparation of 1,4-Benzoquinone Monoketals via Anodic Oxidation of 1,4-Dimethoxybenzenes

Abstract Anodic oxidation of a series of 1-substituted-2,5-dimethoxybenzenes gives 2-substituted-1,1,4,4-tetramethoxycyclohexa-2,5-dienes in almost quantitative crude yield. Selective monohydrolysis of these bis-ketals is possible in many cases, and gives 3-substituted-4,4-dimethoxycyclohexa-2,5-dienones in good to excellent overall yield.

Facile synthesis of novel 2-hydroxytetrazole derivatives via selective N-2 oxidation

Abstract A highly selective oxidation of the sodium salt of ethyl tetrazole-5-carboxylate is reported which produces a novel class of hydroxytetrazole derivative which can then be converted to 2-hydroxytetrazole. A novel preparation of 1-hydroxytetrazole is also reported.