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

Use of aziridines for the stereocontrolled synthesis of (-)-LL-C10037α, (+)-MT35214, and (+)-4-epi-MT35214

Strategies for the synthesis of the title compounds have been developed using a diastereoselective aziridination reaction of 4-O-substituted cyclohexenones. Aziridination using a chiral amine permitted resolution of a 4-hydroxycyclohexane derivative, and this resulted in the synthesis of both enantiomers of the title compound. Alternatively, the chiral 4-hydroxycyclohexenone starting material was derived from quinic acid. In both cases stereoselective epoxidation and opening of the aziridine ring with hydrazoic acid afforded the 2-azidocyclohexenone, which was transformed to the 2-acetamido group present in the natural product.

Absolute Configuration of Natural Cyclohexene Oxides by Time Dependent Density Functional Theory Calculation of the Optical Rotation: The Absolute Configuration of (−)-Sphaeropsidone and (−)-Episphaeropsidone Revised

The optical rotatory power of some natural cyclohexene oxides, such as (+)-chaloxone, 1, (+)-epiepoformine, 2, (+)-epoformine, 3, (+)-epoxidone, 5, (-)-sphaeropsidone, 6, (-)-episphaeropsidone, 7, and the synthetic compound (+)-epitheobroxide, 4, has been calculated by means of the TDDFT/B3LYP method using the 6-31G(d) and aug-cc-pVDZ basis sets, both in the gas phase and in solution by means of the polarizable continuum model. For compounds 1 and 2, which possess high (about 300 units) optical rotations, gas-phase calculations with the smaller basis set are able to reproduce the experimental values both in sign and order of magnitude. By contrast, a larger basis set is required to satisfactorily simulate the OR values of 3 and 4, which show smaller (about 100 units or less) rotations. The inclusion of the solvent effects is different for different compounds; for 1 and 2, it leads to a better agreement between experiment and prediction, while for 3 and 4, the presence of hydrogen bonding groups makes the application of continuum solvation models less satisfactory. For the flexible system 5, the absolute configuration could not be determined using gas-phase calculations and the smaller basis set, but both inclusion of solvent and larger basis set effects are compulsory. It is noteworthy that calculations both in the gas phase and in the solvent lead to a positive rotatory power for the laevorotatory natural compounds 6 and 7 if the ACs reported in the literature are employed to do the theoretical prediction. This strongly indicates that the ACs previously assigned to these compounds in the literature are not correct and that the TDDFT prediction of OR values has become by now a practicable tool for AC assignments.

New stereoselective route to the epoxyquinol core of manumycin-type natural products. Synthesis of enantiopure (+)-bromoxone, (-)-LL-C10037 alpha, and (+)-KT 8110

A practical route is decribed for the preparation of the C(7)N core of manumycin-type compounds. Starting from p-benzoquinone, optically pure compounds in both forms can be prepared via enzymatic resolution of a derived diacetoxy conduritol. A diepoxy aminoinositol is accessible which can function for formation of enantiopure epoxyquinones and quinols. Examples are given for acylation reactions of this amine with several acyl derivatives. With this approach (-)-LL-C10037alpha and quinones such as (+)-KT-8110 with 5R,6S-configuration can be synthesized through oxidation. In addition a short route to (+)-bromoxone is described. Most steps include simple epoxide formation and cleavage reactions which all can be carried out in a high stereoselective manner.

Synthesis of anti-rheumatic agent epoxyquinomicin B

Anti-rheumatic agent (+/-)-epoxyquinomicin B was synthesized for a 22% overall yield in eight steps from commercially available 3-hydroxy-4-nitrobenzaldehyde via the intermediate quinone 6 prepared by selective phenol oxidation of 5 by use of Fremy's salt as the key step.