STEREOCHEMICAL COURSE OF THE [4-METHOXYBUTA-1,3-DIENE TO N-GLYOXYLOYL-(2R)-BORNANE-10,2-SULTAM - THE FORMAL SYNTHESIS OF COMPACTIN AND MEVINOLIN(2] CYCLOADDITION OF 1)

The chiral heterodienophile N-glyoxyloyl-(2R)-bornane-10,2-sultam 2, r eadily prepared from (2R)-bornane-10,2-sultam 1, was used in noncataly zed atmospheric and high-pressure as well as in [Eu(fod)(3)]-catalyzed [4 + 2] cycloadditions with 1-methoxybuta-1,3-diene 3. All the [4 + 2 ] cycloadditions studied led to diastereoisomeric mixtures of 6-substi tuted derivatives of 2-methoxy-5,6-dihydro-2H-pyran 4-7. The extent of asymmetric induction in these reactions was established by H-1 NMR an alysis and the absolute configuration of the thermodynamically stable products 5 and 7 by X-ray analysis, and independently by chemical corr elation. Stereochemical models for both noncatalyzed and [Eu(fod)3]pro moted reactions are proposed. The [4 + 2] cycloadduct 5 was then effec tively transformed into (4R)-hydroxy-(GS)-hydroxymethyltetrahydropyron e-2 12, a key synthon for the lactone moiety of compactin 10 and mevin olin 11. Copyright (C) 1996 Elsevier Science Ltd