An efficient and practical preparation of optically active syn-1-vinyl-2-amino alcohol derivatives by the regio- and diastereoselective addition reaction of (γ-alkoxyallyl)titaniums with chiral imines. Formal synthesis of statine

The pyrrolo[2,1-a]isoquinoline alkaloids

The present chapter describes isolation, biogenetic proposals, and syntheses of the natural products 1-4 and 10-11 with a pyrrolo[2,1-a]-isoquinoline framework. Moreover, the syntheses of some structural analogs are discussed. The pyrrolo[2,1-a]isoquinolines are of interest due to their promising biological activities. For crispine A (1), many total syntheses have been reported and for trolline (3), only three. Only one total synthesis has been reported for each of the following natural products: peyoglutam (10), mescalotam (11), and the antitumor active crispine B (2). Some of the pyrrolo[2,1-a]isoquinoline alkaloids have not been synthesized yet. The following three tables summarize the synthetic efforts toward crispine A (1) (Table 1: racemic syntheses; Table 2: enantioselective syntheses) and trolline (3) (Table 3).

Gram-scale synthesis of (+)- and (-)-trans-10-amino-9-hydroxy-9,10-dihydrophenanthrene by enzymatic hydrolysis

The enzymatic resolution of (+/-)-trans-10-azido-9-acetoxy-9,10-dihydrophenanthrene by Candida cylindracea lipase-catalyzed hydrolysis was achieved on the gram-scale with excellent yield and enantiomeric excess. The resulting (+)- and (-)-amino alcohols were derivatized to alpha-hydroxy-N-benzenesulphonamides.

Asymmetric syntheses of new functionalized beta-amino alcohols via diastereoselective addition of organometallic reagents onto oxazolidines

Diastereoselective reactions between (S)-phenylglycinol-derived oxazolidines and two unsaturated organolithium reagents afforded chiral beta-amino alcohols having vinyl and alkynylsilane moieties. When the same reactions were performed in the presence of titanium isopropoxide, a dramatic change of regioselectivity was observed, from the alpha- to the gamma-position, thus producing beta-amino alcohols with allyl or allenylsilane functions. A rationalization of the observed diastereoselectivity was suggested for each case.

An allyltitanium derived from acrolein 1,2-dicyclohexylethylene acetal and (eta(2)-propene)Ti(O-i-Pr)(2) as a chiral propionaldehyde homoenolate equivalent that reacts with imines with excellent stereoselectivity. An efficient and practical access to optically active gamma-amino carbonyl compounds

A chiral allyltitanium compound 2, prepared in situ by the reaction of optically active acrolein 1,2-dicyclohexylethylene acetal (3) with (eta(2)-propene)Ti(O-i-Pr)(2) (1), reacts with a variety of acyclic and cyclic imines 4 in a regiospecific way to afford alpha-addition products 5 as a mixture of the E- and Z-isomers in good combined yield, where the former is predominant in a ratio of 92:8 to >95:5. The mixture of (E)- and (Z)-5 and pure (E)-5 which could be isolated in several cases were respectively converted to the corresponding beta-amino ester 6 to confirm the absolute configuration and enantiomeric purity. The ee of the newly formed asymmetric center of 5 is more than 78% for the mixture of (E)- and (Z)-5 and more than 96% for pure (E)-5. By taking advantage of the versatility of the vinyl ether moiety in 5, optically active gamma-amino aldehydes 8, gamma-amino aldehyde acetals 7 and 10, gamma-amino acids 9, beta-amino esters 6, and pyrrolidinoisoquinolines 12 were readily prepared. In the reaction of 2 with optically active alpha-silyloxyimine 4n, remarkable double stereodifferentiation was observed; thus, the reaction of 2 derived from (S,S)- or (R,R)-3 provided syn- and anti-5n in a ratio of 55:45 or 0:100, respectively. Meanwhile, the stereochemistry of the product in the reaction of 2 with beta-silyloxyimine 4o was controlled mainly by 2. Thus, the reaction of beta-silyloxyimine 14 with 2 derived from 1 and (R,R)-3 afforded gamma-silyloxyimine 15 with 92% diastereoselectivity, from which 4-amino-6-hydroxypentadecanal dimethyl acetal (13), a key intermediate for the synthesis of batzelladine D, was synthesized.