Aldehydes serine-derived

Amino acid synthesis from aldehydes and hydantoin (Bergmann), synthesis of serine derivatives (Erlenmeyer) or of y-hydroxyaminoacids (Plochl)... 

On the other hand, following the same sequences from the differently protected serine-derived nitrone 168, through the formation of hydroxylamines 169, C2 epimers of carboxylic acid and aldehydes are obtained, i.e., (2S,3R)-170 and (2S,3R)-171. Moreover, the syn adducts 164 were exclusively obtained in the addition of Grignard reagents to the nitrone 163, whereas the same reactions on nitrone 168 occurred with a partial loss of diastereoselectivity [80]. Q, j6-Diamino acids (2R,3S)- and (2R,3R)-167 can also be prepared from the a-amino hydroxylamines 164 and 169 by reduction, deprotection and oxidation steps. The diastereoselective addition of acetylide anion to N,N-dibenzyl L-serine phenyhmine has been also described [81]. 

OXAZOLIDINYL]-2-tert-BUTYLDIMETHYLSILOXYETHANAL FROM A SERINE-DERIVED ALDEHYDE... 

DIASTEREOSELECTIVE SYNTHESIS OF PROTECTED VICINAL AMINO ALCOHOLS (S)-2-[(4S)-N-TERT-BUTOXYCARBONYL-2.2-DIMETHYL-1,3-OXAZOLIDINYL1-2-TERT-BUTYLDIMETHYLSILOXYETHANAL FROM A SERINE-DERIVED ALDEHYDE. 

The direct homologation technique was then extended to the synthesis of various uncommon carbohydrate structures. Thus, higher sugars of the L-series were obtained Starting from 2,3-0-isopropylidene-4-O-benzyl-L-threose (43) [39c] (Scheme 13), and the amino tetrose 47 and pentose 48 were prepared from the a-amino aldehyde 46 derived from L-serine [46a] (Scheme 14). These amino sugars were used as chiral building blocks for the... 

The reaction of N-(terf-butoxycarbonyl)leucinal 2-41 a by Danishefsky et al. with l-methoxy-3-trimethylsilyloxy-l,3-butadiene 2-10 gave the pyrones 2-42 and 2-43 with an induced diastereoselectivity of 9 1 in favour of the syn-com-pound in the presence of Eu(hfc)3 [96]. Later Garner [97] used a N-Boc-serine derived aldehyde 2-41 b and Danishefsky s diene 2-10. In both cases a chelation-control forming a complex between the nitrogen and the oxygen could explain the obtained selectivity. In the presence of HMPA chelation is minimized to give a higher extent of the anfi-product 2-43 (Fig. 2-12) [97]. 

Poll and Sames [112] have converted L-serine into A -methylfucosamine (Scheme 13.63). The method relies on the diastereoselective addition of propenyllithium to the aldehyde derived from protected L-serine derivative 183, giving allylic alcohol 184. Catalytic osmylation of 184 gives a 6 1 mixture of anti,syn 185 and syn,syn-2iminotnols. Protection of the triol 185 as its triacetate, reductive methylation and desilylation provides 186. Successive Swern oxidation, methanolysis and benzhydryl group hydrogenation leads to A -methylfucosamine 187. 

An elegant total synthesis of the semiprotected form of lincosamine was realized by Marshall and Beaudoin [116]. An aldehyde derived from destomic acid (6-amino-6-deoxy-L-g/yc ro-D-ga/acto-heptonic acid) was derived in a similar way from a L-serinal derivative via hetero Diels-Alder addition to 1-ethoxy-3-[(trimethylsilyl)oxy]-4-benzyloxy-1,3-butadiene [142]. A similar method was applied to the preparation of a semiprotected form of anhydrogalantinic acid, a component of the antibiotic galantin I [142]. 

As the structure of the side chain of the pyrimidine moiety remained uncertain until the very final stage of the structure elucidation, we proceeded to synthesize the most probable candidate for the structure of this moiety to compare with the natural sample. Relevant methodology was required to acquire the skeleton of BLM and we found a new synthon diethoxyacetamidine (8) for the efficient preparation of multifunctional pyrimidine (9), which was readily converted into the key aldehyde (10) (Fig. 10) [37]. The p-aminoalanin-amide moiety (7) was synthesized by Mitsunobu reaction of serine derivative (6)... 

Diamino-2,4-dideoxy-L-arabinose and -L-ribose, 75 and 76 respectively, were obtained in similar quantities by chain extension of the L-serine-derived aldehyde 74 as shown in Scheme 17. The imino-sugar glycosylamide 78 was... 

The aminoalditol 23 was prepared by a pinacol-like homocoupling of an appropriately protected L-serine-derived aldehyde and promoted by a vanadium-zinc complex [V2Cl3(THF)6)]2[Zn2Cl6]. (See Section 2.2 for the further transformation of compound 23). 

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