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An efficient approach to access α-arylacetylene-substituted pyrrolidine and piperidine derivatives has been developed through a samarium diiodide-mediated addition–elimination process of N-α-radicals with arylacetylene sulfones.

An efficient approach to functionalized 4,6-disubstituted-and 4,6,6-trisubstituted-1,3-oxazinan-2-ones skeleton has been developed through the reaction of semicyclic N, O-acetals 4a and 4b with 1,1-disubstituted ethylenes 5 or 8. As a result of such a [4 + 2] cycloaddition process, 4,6,6-trisubstituted-1,3-oxazinan-2-ones 6aa, 6af-6au, 7ba, 7bf-7bw and 6,6-spiro containing 1,3-oxazinan-2-ones 9ad, 9ae, 10ba-10bg were obtained in 36%-96% yields and with moderate to excellent diastereoselectivities. In addition, the synthesis of (±)-norallosedamine 12 could be conveniently achieved from the cycloadduct 7bf.

An efficient approach to access α-arylacetylene-substituted pyrrolidine and piperidine derivatives has been developed through a samarium diiodide-mediated addition-elimination process of pyrrolidine and piperidine

A novel approach to 2-substituted-2-(dimethoxyphosphoryl)-pyrrolidines 7a-7o and 9a-9r has been developed, which features a TMSOTf-mediated one-pot intramolecular cyclization and phosphonylation of substituted tert-butyl 4-oxobutylcarbamates. The major advantages of this method include simple operation under mild reaction conditions, the use of cheap Lewis acid, and good to excellent yields with high diastereoselectivities (dr up to 99:1).

An efficient approach to access functionalized (2,3-dihydroisoxazol-4-yl) ketones has been developed by reacting nitrones 4 with ynones 7 or terminal ynones 10 in a one-pot fashion. The reaction went through a formal Sc(OTf)3-catalyzed [3 + 2]-cycloaddition process to generate a number of functionalized (2,3-dihydroisoxazol-4-yl) ketones 11aa–11aw, 11ba–11la and 12aa–12ae in moderate to good yields.

The Cu(OTf)2 catalyzed Ugi-type reactions of N,O-acetals with isocyanides have been described for the synthesis of pyrrolidinyl and piperidinyl 2-carboxamides. 4-Hydroxy-5-substituted-prolinamides can be obtained in high diastereoselectivities (2,4-cis/trans > 19 : 1) and a stereoselective model was proposed for 2,4-cis selectivity. Moreover, 4-F-VH 032, a novel analog of the VHL ligand, was conveniently obtained by utilizing the present method.

An approach to access functionalized 3,4-dihydro-1,3-oxazin-2-ones has been developed by reacting semicyclic N,O-acetals 5 and 6 with ynamides 7 or terminal alkynes 8 in a one-pot fashion. The reaction went through a formal [4 + 2] cycloaddition process to generate a number of functionalized 3,4-dihydro-1,3-oxazin-2-ones 9a-9ak and 10a-10bc in yields of 34-97%. In addition, the utility of this transformation was demonstrated by the synthesis of (±)-sedamine 13.

A highly efficient gold-catalyzed approach between N,O-acetals and ynamides for the construction of 6-(tert-butyldimethylsilyl)oxy-tetrahydropyrrolo[1,2-c][1,3]oxazin-1-ones was developed. This rea...

A highly regioselective approach to access amide enol carbamates and carbonates 5a-5c', 7a-7h, and 9 was developed through Cu(OTf)2-catalyzed reactions of ynamides 4 with t-butyl carbamates 2 and 8 and t-butyl carbonates 6. Moreover, this strategy was successfully applied to generate amide enol carbamates 11a-11s and 14a-14f from imides 10 and 13 with ynamides through an N-Boc cleavage-addition ring-opening process. A range of substituents was amenable to this transformation, and the desired amide enol carbamates and carbonates were obtained in moderate to good yields.

Regioselective C-H alkenylation of

The Cu(OTf)

A novel approach to 2-substituted-2-(dimethoxyphosphoryl)-pyrrolidines

A diastereoselective approach to obtain amino alcohols 10 through SmI2-induced radical addition of chiral imine 8 with 2-(benzyloxymethylsulfonyl)pyridine 9 is described. This approach was easily used for the synthesis of non-natural amino acid 15, a flexible key fragment whose utility was demonstrated in the divergent synthesis of dolastatin 10 (1) and its nine analogues 31a, 31c, 31d, 31e, 31f, 31g, 40a, 40b and 40c were obtained.

A new approach to access 1-benzylisoindoline and 1-benzyl-tetrahydroisoquinoline has been developed through nucleophilic addition of organozinc reagents to N,O-acetals. A number of substituted organozinc reagents were amenable for this transformation, and the desired products were obtained with excellent yields. Moreover, Sc(OTf)3 proved to be an effective catalyst for the formation of 1-benzylisoindoline and 1-benzyl-tetrahydroisoquinoline using such nucleophilic addition.

An efficient approach to access functionalized tertiary-type β-hydroxyl carboxamides has been developed through Sc(OTf)3-catalyzed addition of ynamides and substituted ketones. Water was found to be an important reaction substrate, and the solvent was not needed in this process. A broad range of substituted ynamides and ketones was well applicable to the reaction with excellent chemical selectivities. Moreover, several chiral β-hydroxyl carboxamides 3j–3r were prepared with excellent regioselectivities and outstanding diastereoselectivities.

An efficient approach to access functionalized 1,4- and 1,5-amino alcohols has been developed through the nucleophilic addition of semicyclic N,O-acetal with organozinc reagents. A number of substi...

The first Ni(OTf)2-catalyzed hydroamination of ynamides 2 was developed by reacting with secondary amines (1 and 4). This protocol features excellent regioselectivity, a broad substrate scope of secondary aryl amines, and good functional group tolerance for ynamides. Using this method, a variety of substituted ethene-1,1-diamine compounds were prepared in moderate to excellent yields with high regioselectivities.

An efficient approach to a functionalized bicyclo[2.2.2]octan-2-one scaffold has been developed through a one-pot cascade process including amino acid involved successive Michael addition and decarboxylative-Mannich sequence. Starting from α,β-unsaturated ketones and amino acids, a series of desired products 7a-7m and 8a-8o were obtained with moderate yields. In addition, the tandem process was reasonably explained by the results of DFT calculations.

An efficient approach to access functionalized (2,3-dihydroisoxazol-4-yl) ketones has been developed by reacting nitrones 4 with ynones 7 or terminal ynones 10 in a one-pot fashion. The reaction went through a formal Sc(OTf)3-catalyzed [3 + 2]-cycloaddition process to generate a number of functionalized (2,3-dihydroisoxazol-4-yl) ketones 11aa-11aw, 11ba-11la and 12aa-12ae in moderate to good yields.

An approach to access functionalized 3,4-dihydro-1,3-oxazin-2-ones has been developed by reacting semicyclic

A highly efficient gold-catalyzed approach between

A zinc-catalyzed decarboxylative A3 reaction of cyclic amino acids, α,β-unsaturated aldehydes and terminal alkynes has been developed. A series of functionalized N-heterocyclic 1,6-enynes have been successfully obtained with excellent regioselectivities through this novel approach. In addition, the utility of this straightforward process is demonstrated by the preparation of a polycyclic nitrogen-containing heterocyclic compound.

An efficient diastereoselective approach to access (4R)-hydroxy-(2S)-substituted methyl ketones pyrroles skeleton 4a-s has been developed through Mannich process involving N,O-acetal 6 and ketones and propionaldehyde in excellent yield with high diastereoselectivity (dr up to 99:1). In addition, the utility of this convenient Mannich process is demonstrated by the diastereoselective synthesis of Tuv fragment (2) and its analogue (18) of tubulysin V (1e).

An approach to access 1-substituted isoquinolones has been developed through the addition–cyclization of imines with Grignard reagents in the presence of 2,2′-dipyridyl. A number of substituted aromatic magnesium reagents were amenable to this process, and the desired products were obtained with excellent yields and outstanding diastereoselectivities (dr > 99:1). The utility of this convenient approach is demonstrated by the formal synthesis of (S)-cryptostyline II. Moreover, N-methylmorpholine (NMM) was found to be an effective additive for the formation of 3-substituted isoindolin-1-ones using one-pot addition–cyclization–deprotection of imine with Grignard reagents.

An efficient diastereoselective approach to access trans-5-hydroxy-6-substitutedethanone-2-piperidinones skeleton has been developed through sequential addition-deprotection-cyclization process involving aldimine 6 with substituted acetones. The diastereoselectivity of substitution at C-6 position of 2-piperidinone was controlled by α-siloxyl group and chiral sulfinamide moiety. In addition, the utility of this effective approach is demonstrated by the scalable syntheses of (+)-febrifugine (2) and (+)-halofuginone (4).

An efficient diastereoselective approach to access trans-5-hydroxy-6-substituted 2-piperidinones skeleton has been developed through one-pot intramolecular tandem process of O-benzyl protected aldimine 11 with Grignard reagents. The diastereoselectivity of substitution at C-6 position of 2-piperidinone was controlled by α-benzyloxy group. In addition, the utility of this straightforward cascade process is demonstrated by the asymmetric syntheses of (+)-L-733, 060 (2) and its 2-substituted analogue 3, as well as (+)-CP-122721 (5).

An efficient approach to access functionalized tertiary-type β-hydroxyl carboxamides has been developed through Sc(OTf)

A zinc-catalyzed decarboxylative A

An efficient approach to access functionalized 1,4- and 1,5-amino alcohols has been developed through the nucleophilic addition of semicyclic

An efficient approach to access functionalized dihydro-[1,3]oxazino[4,3-a] isoindole and tetrahydroisoquinoline skeletons has been developed through the addition-cyclization process of ynamides 8 with N-acyliminium ions generated from N,O-acetals 6,7. The reactions were conducted under the catalysis of Cu(OTf)2, and a number of functionalized dihydro-[1,3]oxazino[4,3-a] isoindoles 9a-9y and tetrahydroisoquinolines 10a-10g, 11a-11p were generated in 48–98% yields. When chiral ynamides 8n-8u were used, optically pure products 11a-11p could be obtained with good to excellent yields and diastereoselectivities.

An effective approach to access dyadic 1,3-oxazinan-2-ones 8a-8c and 4,4a,5,6-tetrahydro-[1,3]oxazino[3,4-a]quinolin-1(3H)-ones 8d-8h was developed through Sc(OTf)3-catalyzed intramolecular cyclization from tert-butoxycarbonyl to acyliminium ion 7a-7j. A variety of substituted N,O-acetals, with different ring size, proved to be suitable substrates for this transformation, and a series of (4aS,6S,7R)-6-OTBS-7-substituted-hexahydropyrrolo[1,2-c][1,3]oxazin-1-ones 11a-11j and other chiral dyadic 1,3-oxazinan-2-ones 8i, 8j, 11k were synthesized in moderate yields with excellent diastereoselectivities (dr > 99:1). Moreover, 2,5-trans-products 11a-11j were obtained through this interesting Lewis acid-catalyzed intramolecular cyclization process.

Dolastatin 10, an antineoplastic agent for cancer chemotherapy, is a linear peptide possessing N,N-dimethyl Val-OH, L-valine, (3R,4S,5S)-dolaisoleucine, (2R,3R,4S)-dolaproine and (S)-dolaphenine. Our efficient synthesis includes the following three key features: (1) SmI2-induced cross-coupling was employed to couple aldehyde 11 with (S)-N-tert-butanesulfinyl imine 12 to generate the required stereocenters of Dap (7); (2) asymmetric addition of chiral N-sulfinyl imine 10 provided a straightforward approach to the synthesis of the protected Doe ((S,S)-8); (3) a practical method to the key subunit Val-Dil (24a) has been established as an alternative synthetic route for the synthesis of this challenging chemical structure.

A diastereoselective approach to trans-4-hydroxy-5-substituted 2-pyrrolidinones 1 (P1 = TBS, P2 = H) has been developed through a stereoselective tandem Barbier process of (R,SRS)-8 with alkyl and aryl bromide. The stereochemistry at the C-5 stereogenic center of the trans-4-hydroxy-5-substituted 2-pyrrolidinones was solely controlled by α-alkoxy substitution. This effective approach was successfully used to prepare a variety of substituted (3R,4S)-statines 2. In addition, two bioactive natural products of (+)-preussin 4 and hapalosin 5 were effectively synthesized through this stereoselective tandem Barbier process.

An efficient method for asymmetric synthesis of epohelmins A (3), B (4) and their isomer 24 is detailed in this report. The key feature in this divergent synthesis includes the SmI2-induced cross-coupling of N-tert-butanesulfinyl imine 10 with chiral aldehyde 9 derived from d -malic acid. A cascade cyclization to the pyrrolizidine skeleton is achieved in our synthetic route for epohelmins. In addition, an interesting intramolecular oxa-Michael addition was observed for epohelmin A (3).

A convenient method for diastereoselective synthesis of the key intermediate 5 from triheterocyclic fragment and polyketide 6 for hoiamides A (1) and B (2) was developed. The main feature is the successive construction of four stereogenic centers from C33 to C36 for hoiamides A (1) through the well-established Oppolzer’s anti-aldol and Paterson’s anti-aldol methodology. Furthermore, asymmetric allylation was also utilized as a key step to form the stereogenic center at C32 for hoiamides A (1).

Tubulysin V has been enantioselectively synthesized from the units of dipeptide 23, Tuv and Tup. The features of this synthetic strategy is included three portions, the Tuv fragment 17 was diastereoselectively synthesized from the d -malic acid, the stereocenters of the Tup unit was constructed by the asymmetric reduction as well as methylation, and the epimerization for several known methods was successfully avoided by condensation of fragment 19 with 24, and by deprotection with hydrogenation.

An efficient approach to access functionalized 3-alkenylindoles has been developed through Er(OTf)3-catalyzed addition of ynamides and indoles. A number of C-aryl substituted ynamides 7a-7k could react with indoles 6a-6s, affording the desired products 8aa-8sa, 8ab-8ak, 8bd, 8bk and 8tc in moderate to excellent yields with high regioselectivities.

An efficient approach to access chiral 3-tert-butyl-dimethylsiloxy 2,6-disubstituted 6-benzyl piperidines was developed through nucleophilic addition of N,O-acetals with organozinc reagents. A number of substituted benzyl zinc reagents could react with N,O-acetals 6a-6e, affording the desired products 7a-7j and 9a-9q in good to excellent yields and with high diastereoselectivities.

An efficient asymmetric approach to access functionalized pyrido- and pyrrolo[1,2- c][1,3]oxazin-1-ones has been developed through a nucleophilic addition-cyclization process of N, O-acetal with ynamides. A number of substituted ynamides 8a-8o and 3-silyloxypyrrolidine or piperidine N, O-acetals 6a, 7 were amenable to this transformation, and the desired products 9a-9o, 10a-10m were obtained with excellent regioselectivities and outstanding diastereoselectivities. Moreover, chiral ynamides 14a-14f could also experience this addition-cyclization process to afford products 15a-15f in excellent yields.

An efficient approach for asymmetric synthesis of (+)-spicigerine, (+)-cassine and their 3-epimers has been developed through the intramolecular diastereoselective tandem addition/cyclisation process of α-chiral aldimine 9 with methylmagnesium bromide and the asymmetric addition of nucleophilic reagents to aminal 14. Moreover, the first asymmetric synthesis of (+)-spicigerine has been achieved in this manuscript. In this synthetic strategy, the asymmetric syntheses of (+)-spicigerine and (+)-cassine was achieved in a 14% overall yield and nine steps and an 18% overall yield and seven steps from cheap α-chiral aldimine 9, respectively.

A diastereoselective new approach for the synthesis of trans-4-hydroxy-5-allyl-2-pyrrolidinone 9 has been developed through In-mediated allylation of α-chiral aldimine 8 with allyl bromide. The stereochemistry at the C-2 stereogenic center of 9 was controlled by both the α-OTBS substitution and the sulfinamide moiety. The utility of this asymmetric allylation is demonstrated by the asymmetric syntheses of epohelmins A (4) and B (10).

The one-pot tandem process of ( 2R,4R,S RS )- 15 with Grignard reagents for highly diastereoselective synthesis of functionalized 2-piperidinone 1 was developed. Furthermore, the divergent syntheses of L-685,458 3 and its six analogues 20a – f have been conveniently achieved using this effective protocol as the key step.

An efficient and step-economical approach to access functionalized pyrrolizidine derivatives by a one-pot tandem sequence, including an aldol condensation and subsequent 1,3-dipolar cycloaddition process, has been developed, starting from acetone, aldehyde, and proline. A number of substituted aromatic aldehydes were amenable to this transformation, and the desired products, racemic 7a–7w and chiral 9a–9m, were obtained with excellent regioselectivities and outstanding diastereoselectivities. Moreover, in situ NMR studies revealed MgSO4 could effectively promote the aldol condensation pathway in this tandem process.

A highly diastereoselective approach for the synthesis of trans-4-hydroxy-5-substituted 2-pyrrolidinones has been developed through an intramolecular cascade process of α-chiral aldimines using alkyl, aryl, alkynyl, and alkenyl Grignard reagents. The stereochemistry at the C-5 position of 2-pyrrolidinone after reaction with alkyl, aryl, and alkenyl Grignard reagents was solely controlled by α-alkoxy substitution. For alkynyl Grignard reagents, the stereochemistry was controlled by coordination of the α-alkoxy substitution and the stereochemistry of the sulfinamide. The utility of this one-pot cascade protocol is demonstrated by the asymmetric synthesis of streptopyrrolidine 5 and 3-epi-epohelmin A 3-epi-6.