SummaryThree methods are described by which diastereomerically enriched nitroaldols and their O-silylated derivatives can be prepared. threo-Nitroaldols prevail up to 10: 1 over the erythro-isomers if doubly deprotonated nitroaldols 28 are quenched with acetic acid (THF/HMPT or DMPU, -looo) (see Scheme 5 and Table 2). O-Trimethyl-or O-(f-butyl)dimethylsilylated (TBDMSi) erythro-nitroaldols can be obtained by protonation of the corresponding lithium nitronates (35, 39) in THF at low temperature (see Schemes 6 and 7). The erythro-O-TBDMSi-nitroaldol derivatives are also formed in the fluoride catalyzed addition of TBDMSi-nitronates (40-45) to aldehydes (see Schemes 8 and 9). In the latter reaction no 1,2-asymrnetric induction is observed if a-branched silylnitronates or aldehydes are employed (see 48/49 and 50/51). -The stereochemical course of the reactions leading to erythro-O-TBDMSi-nitroaldols follows topological rules of broad applicability (see Scheme 10); possible mechanisms are discussed. -The configuration of erythro/ threo-nitroaldols is determined by chemical correlation (see 24-26) and by I3C-NMR. spectroscopy. -Some examples of the preparation of diastereomerically enriched 1,2-aminoalcohols by reduction of the corresponding nitro compounds without loss of configurational purity are described (see Schemes I 1 and 12).A) Introduction. -The nitroaldol-or Henry reaction is one of the classical C,Cbond forming processes. It furnishes the 1,2-functionalized nitroalcohols 1, precursors of the symmetrical (R' = R2) and unsymmetrical (R' # R2) aminoalcohols 2.Nitroaldols have been extensively reviewed [3] [4], and have frequently been used as intermediates in synthesis. However, the lack of stereoselectivity in the Henry reaction (except in cyclic systems) has hardly been mentioned. This lack of selectivity is due to the reversibility of the reaction and the easy epimerization at the nitro-substituted C-atom. The nitroaldols of type 1 (R',R2#H) occur in two dia-

The cyclic urea DMPU ( N , N'-dimethyl-N, N'-propylene urea= 1,3-dimethyl-2-0x0-hexahydropyrimidine) is shown to exhibit the same effects as HMPT in oxirane-opening with Li-acetylide, in a Wittig olefination, in the double deprotonation of a nitroalkane, in the Michael addition of Li-dithiane to cyclohexenone, and in selective generations of certain enolates (Schemes 1-7). DMPU might therefore be a safe substitute of the carcinogenic HMPT as a cosolvent with unique properties in diverse types of reactions.Hexamethylphosphoric triamide (HMPT) is extensively used in research laboratories due to its unique properties as a dipolar aprotic solvent [l] and its superior ability to form cation-ligand complexes [ 2 ] . However, in recent years HMPT has been sholvn to be a carcinogen in animal tests even at low concentrations [3] and 'it was concluded that HMPA ranks in the super league of experimental carcinogens and must be considered as potentially posing a serious risk to man, even at the scale of use in a laboratory ' [4]. The need for a safe substitute is thus indispensable. Tetrasubstituted ureas1)2) appeared to us especially attractive since their properties are similar to those of HMPT. We were particularly interested in a cosolvent which a) would be compatible with highly nucleophilic and basic reagents3), and b) could be employed at dry-ice temperature or below. We reportFor a review on tetramethylurea, see [5]; for a more recent survey of tetrasubstituted ureas as solvents see [6]. A few other solvents, cosolvents, and/or complexing agents have also been studied; for example tetraalkylsulfamides [7] and N, N, N', N'-tetramethylethylenediamine (TMEDA) 181.Other solvents such as dimethyl sulfoxide (acidic) or 1-methyl-2-pyrrolidinone (both acidic and electrophilic) were thus not suitable.

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Mulundocandin, a new lipopeptide antibiotic, was isolated from the culture broth of a strain of Aspergillus sydowi No. Y-30462.The antibiotic, obtained as a colorless amorphous powder having the molecular formula C4SH77N7O16, is an antifungal antibiotic active against yeasts and filamentous fungi.