Suchergebnisse

This Minireview describes the exploitation of certain enzymatically derived, readily accessible, and enantiomerically pure cis‐1,2‐dihydrocatechols as starting materials in the chemical synthesis of a range of biologically active natural products, most notably sesquiterpenoids and alkaloids. ; We thank the Chinese National Natural Science Foundation (Grant 21801094), the Australian Research Council, the Institute of Advanced Studies at the Australian National University and the Fundamental Research Funds for the Central Universities (China) (Grant 21617327) for generous financial support. SY is the grateful recipient of an Australian Government-funded PhD scholarship.

Compound ent-1 as well as certain related homochiral and polyfunctionalized cyclohexenes have been prepared from the 1,2-diacetal 4 that is itself readily derived from L-tartaric acid (3). Grignard addition and ring-closing metathesis processes constitute the key steps associated with the reaction sequences involved. This work provides a method for obtaining a range of potentially useful cyclohexenone-containing chirons that are enantiomerically related to those that have been prepared from the homochiral cis-1,2-dihydrocatechol 2, the product of the microbial biotransformation of bromobenzene. ; We thank the Research School of Chemistry, the Australian Research Council and Institute of Advanced Studies for support. JNB is the grateful recipient of an Australian Postgraduate Award (APA) provided by the Australian Government.

Compound ent-1 has been prepared by engaging a derivative of the enantiomerically enriched and microbially derived cis-1,2-dihydrocatechol 6 in an intramolecular Diels-Alder reaction, elaboration of the adduct so-formed to the cyclopentannulated bicyclo[2.2.2]octenone 3, and photochemical rearrangement of this to the cyclobutanone 2. By such means it has been established that 4,12-dihydroxysterpurene (1) is not the structure of the natural product isolated by Xie and co-workers from a culture broth of Stereum purpureum. ; We thank the Australian Research Council and the Institute of Advanced Studies for financial support. P.L. is the grateful recipient of a CSC Ph.D. Scholarship provided by the Government of the People's Republic of China.

Compound ent-1 has been prepared by engaging a derivative of the enantiomerically enriched and microbially derived cis-1,2-dihydrocatechol 6 in an intramolecular Diels-Alder reaction, elaboration of the adduct so-formed to the cyclopentannulated bicyclo[2.2.2]octenone 3, and photochemical rearrangement of this to the cyclobutanone 2. By such means it has been established that 4,12-dihydroxysterpurene (1) is not the structure of the natural product isolated by Xie and co-workers from a culture broth of Stereum purpureum. ; We thank the Australian Research Council and the Institute of Advanced Studies for financial support. P.L. is the grateful recipient of a CSC Ph.D. Scholarship provided by the Government of the People's Republic of China.

A total synthesis of compound 3 from D-(−)-tartaric acid is reported, thereby establishing that the structure, including relative stereochemistry, originally assigned to the cyclic carbonate-containing natural product aspergillusol B is correct. ; We thank the Australian Research Council and the Institute of Advanced Studies for financial support. J.N.B. is the grateful recipient of an APA Scholarship provided by the Australian Government.

The alcohol 12, which is available in eight steps from the enzymatically derived cis-1,2-dihydrocatechol 8, engages in an intramolecular alkoxy radical-mediated remote functionalization reaction to form the tetrahydrofuran 13, thus establishing the perhydro-3,5a-methanoindeno[4,5-c]furan framework associated with the biologically active tashironins. Various manipulations of compound 13 and certain derivatives allow for the formation of compounds bearing strong structural resemblances to the title natural products. ; We thank the Australian Research Council and the Institute of Advanced Studies for financial support and Dr. Brett Schwartz for a great deal of useful advice. M.K.S. is the grateful recipient of an Australian Government Endeavour Award.

The alcohol 12, which is available in eight steps from the enzymatically derived cis-1,2-dihydrocatechol 8, engages in an intramolecular alkoxy radical-mediated remote functionalization reaction to form the tetrahydrofuran 13, thus establishing the perhydro-3,5a-methanoindeno[4,5-c]furan framework associated with the biologically active tashironins. Various manipulations of compound 13 and certain derivatives allow for the formation of compounds bearing strong structural resemblances to the title natural products. ; We thank the Australian Research Council and the Institute of Advanced Studies for financial support and Dr. Brett Schwartz for a great deal of useful advice. M.K.S. is the grateful recipient of an Australian Government Endeavour Award.

Hydrogenolytic cleavage of the ring-fused cyclopropane 11 using hydrogen in the presence of platinum oxide afforded the gem-dimethylated cyclohexane 12 in 99 % yield. In contrast, analogous treatment of congener 13 afforded only trace amounts of the targeted and gem-dimethylated sesquiterpene (+)-viridianol (1), the major products of reaction now being the vic-dimethylated compound 14 and the 2-fold ring-cleavage product 15. ; The authors thank the Australian Research Council and the Institute of Advanced Studies for financial support. FT and PL are the grateful recipients of funding provided by the CSC of the Government of the People's Republic of China.

A total synthesis of the title sesquiterpene 4 is described that starts with the chiral, non-racemic cis-1,2-dihydrocatechol 10 obtained through the whole-cell biotransformation of p-iodotoluene. Compound 10 is elaborated over seven steps, including Negishi cross-coupling and intramolecular Diels–Alder (IMDA) cycloaddition reactions, to ketone 7 that engages in a photochemically promoted 1,3-acyl migration and so affording cyclobutanone 6. Compound 6 was converted over further steps into the title compound 4. ; We thank the Australian Research Council and the Institute of Advanced Studies for financial support. F.T. and P.L. are the grateful recipients of funding provided by the CSC of the Government of the People's Republic of China.

A series of enantiomerically pure bicyclo[2.2.2]octenones, including the lactone-annulated system 26, has been prepared by engaging derivatives of an enzymatically derived and homochiral cis-1,2-dihydrocatechol in inter- or intra-molecular Diels–Alder reactions. Systems such as 26 readily participate in photochemically promoted oxa-di-π-methane rearrangement or 1,3-acyl migration processes to give products such as diquinane 34 or mixtures of cyclobutanone 36 and cyclopropane 38, respectively. ; We thank the Australian Research Council and the Institute of Advanced Studies for financial support. Q.Y. is the grateful recipient of a CSC PhD Scholarship provided by the Government of the People's Republic of China.

Pyrolysis of variously pretreated or untreated samples of chitin (1) and certain congeners at 150-350 °C afforded a range of platform molecules, as exemplified by compounds 4, 5, 6, 8, 12 and 13. All of these products have been fully characterized, including by single-crystal X-ray analysis. Pathways for the formation of them are proposed and theoretical studies of certain aspects of these described. ; Funding from the Australian Research Council is gratefully acknowledged (including through Grant Nos. FL170100041 and CE140100012) as is support (to M.N.) from the Islamic Government of Iran.

The title alkaloids, 1 and 2, have been prepared using cross-coupling chemistries and together with various analogues they have been evaluated for their capacity to inhibit acetylcholinesterase. Contrary to an earlier report, it was found that biaryl 1 is not a significant inhibitor of this enzyme, and neither are any of its congeners, including alkaloid 2. ; We thank Jinan University, the Australian Research Council, and the Institute of Advanced Studies for financial support. H. S. K. and G. J. C. are the grateful recipients of scholarships provided by the Australian Government.

On exposure to a combination of Cu[I]- and Pd[0]-based catalysts, compounds such as 1 and 7 engage in tandem Ullmann-Goldberg cross-coupling and cyclopalladation-reductive elimination reactions to give benzofurans such as 8. Related reactions involving hetero-Michael additions of o-halogenated phenols or anilines to propiolates and the Pd[0]-catalyzed cyclization of the resulting conjugates provide, in a one-pot process, alternately functionalized benzofurans, indoles, or phthalanes. ; We thank the Australian Research Council and the Institute of Advanced Studies for financial support including the provision of scholarships to F.K. and M.A. as well as a postdoctoral fellowship to Y.V. F.M. thanks the Higher Education Council of the Government of Pakistan for support, and M.S. acknowledges the support of the Islamic Government of Iran