Synthetic efforts toward cyathane diterpenoid natural products

Abstract

An overview of synthetic efforts toward cyathane diterpenoid natural products from the year 2000 to present is provided. The emphasis of this review is the various ring-constructing and stereoforming strategies employed in these synthetic routes. 1 Introduction 2 Overview of the cyathane diterpenoids 2.1 Isolation 2.2 Bioactivity 2.3 Biosynthesis 3 Strategy summary 4 Cyathane core syntheses 4.1 Wender's cyathane core synthesis 4.2 Desma€ ele's cyathane core synthesis 4.3 Takeda's cyathane core synthesis 5Cyathane total syntheses 5.1 Snider's (AE)-allocyathin B 2 and (+)-erinacine A 5.2 Tori's (AE)-allocyathin B 2 5.3 Piers' (AE)-sarcodonin G 5.4 Ward's (AE)-allocyathin B 3 5.5 Ward's (À)-cyathin A 3 5.6 Nakada's (+)-allocyathin B 2 5.7 Nakada's (À)-erinacine B 5.8 Nakada's (À)-erinacine E 5.9 Trost's (+)-allocyathin B 2 5.10 Danishefsky's (À)-scabronine G 5.11 Phillip's (+)-cyanthiwigin U, (+)-cyanthiwigin W, and (À)-cyanthiwigin Z 5.12 Reddy's (+)-cyanthiwigin AC 5.13 Stoltz's (À)-cyanthiwigin F 6 Conclusions 7 Acknowledgements 8 References

Three new cyathane diterpenoids from the medicinal fungusCyathus africanus

“…In particularly, Cyathus is a genus of medical fungi which belongs to the family Nidulariaceae. Many Cyathus species are noted for their prolific producers of bioactive cyathane diterpenoids with the presence of a characteristic 5-6-7 tricarbocyclic fused core structure [3]. In 1972, Ayer and coworkers first reported the isolation of cyathin A 3 and allocyathin B 3 from the liquid culture of Cyathus helenae [4].…”

7-6-5 Tricarbocyclic Diterpenes

“…Fig. Until 2009, cyathane syntheses have been collected in the excellent reviews of Wright and Whitehead [3] and Enquist and Stoltz [4]. Among them can be seen a valparane derivative, a considerable number of cyathane derivatives, and three verrucosane derivatives.…”

“…After several trials, the authors by reaction of (AE)-320 with vinyldiazoacetate 321 in the presence of Davies's dirhodium tetraprolinate catalysts [Rh 2 ((R)-dosp) 4 ] and [Rh 2 ((S)-dosp) 4 ] achieved 322 and 323 each in !85:15 e.r. as outlined in Scheme 5.7 (Table 5.15 entries 2 and 3).…”

“…In contrast with other families or groups of tricyclic diterpenes (pimaranes, abietanes, totaranes, or cassanes) with the podocarpane tricyclic system 6-6-6 [1], which appear in excellent diterpenoid reviews [2] and are grouped and classified according to their biogenetic origin, 7-6-5 tricyclic diterpenes have never been studied together. Until now, the reviews refer mainly to the synthesis of cyathanes, see Wright and Whitehead [3] and Enquist and Stoltz [4]. In this review, we will examine the 7-6-5 tricyclic diterpenes valparanes, mulinanes, cyathanes, and homoverrucosanes and their epi-derivatives, such as epihomoverrucosanes and gagunins, which have been included with other biogenetic-related groups, including valparolanes, azorellanes, verrucosanes, neoverrucosanes, and epi-neoverrucosanes ( Fig.…”

Enantioselective Synthesis of the 5–6–7 Carbocyclic Core of the Gagunin Diterpenoids

“…2 A general route toward the cyathanes was previously reported by our laboratory using our enantioselective Tsuji allylation methodology. 3 Bis-β-ketoester 9 , comprised of a mixture of racemic and meso diastereomers, was treated with a catalytic amount of Pd 2 (pmdba) 3 and the ligand ( S )- t- Bu-PHOX ( 10 ) 4 to forge two all-carbon quaternary stereocenters in a single operation, affording diketone 11 in 99% ee as a 4.4:1 mixture of ( R , R ) to meso -diastereomers (Scheme 1).…”