On treatment of vinyl chloride epoxide (4) with water, of chloroethylene carbonate (9) with aqueous bases, of vinyl acetate (1) or ethyl vinyl ether (6) with aqueous potassium chlorate and catalytic amounts of osmium tetroxide, glycolaldehyde (5) was formed (scheme 1). The not isolated aldehyde 5, when submitted to the Zelinsky-Stadnikoff amino acid synthesis, afforded rx-serine in 70% yield. The latter method, when applied directly to the "masked glycolaldehydes 2,7,9, 10, vinylene carbonate (ll), 13 or 14, also gave DL-serine (yields 35 -70%), whereas with 4 no serine formation could be detected (scheme 1).Synthesen von DL-Serin und Vorlaufern (Glycolaldehyd und ,,maskierte" Glycoialdehyde) Bei Behandlung von Vinylchloridepoxid (4) mil Wasser, von Chlorethylencarbonat (9) mit wlDrigen Basen, von Vinylacetat (1) oder Ethylvinylether (6) mit wal3rigem Kaliumchlorat und einer katalytischen Menge Osmiumtetroxid bildete sich Glycolaldehyd (5) (Schema 1). Der nicht isolierte Aldehyd 5 lieferte bei der Zelinsky-Stadnikoff-Aminosaure-Synthese DL-Serin mit 70% Ausbeute. Diese Methode ergab, direkt von den ,,maskierten" Glycolalrl-~.~~'.*n ?, 7 9 10. Vinylencarbonat (ll), 13 oder 14 ausgehend, ebenfalls DL-Serin (Ausbeuten 35-70%). wogegen ausgehend von 4 kein Serin nachgewiesen werden konnte.The present paper reports the principal results of a research aimed a t finding commercial syntheses of DL-serine from inexpensive starting materials. O u r interest o n this topic relied on the possibility of developing an industrial process of L-tryptophan preparation from indole and DL-serine using fibre-entrapped tryptophan synthetase I).It is known that DL-serine can be obtained from glycolaldehyde (5) in a yield of 54% by a modified Bucherer-Bergs (B.-B.) reaction') and of 9% by the Strecker method3). However, in preliminary experhents we found that the Zelinsky-Stadnikoff (Z.-S.) modification of the Strecker synthesis allows to prepare serine from 5 in a quite superior yield (70%). It is further known that also 1,1,2-triacetoxyethane4' (7), a "masked" glycolaldehyde which liberates 5 in alkaline medium, affords serine in 70% yields either by the classical B.-lL5' or by the Z.-S.6' procedure. In view of these facts, our research program was developed according to the following lines. (a) Search for inexpensive syntheses of 5 by development of the known ones which appeared to be economically more promising, or by new methods. (b) Search for alternative, economical, syntheses of 7, the known one4) requiring the use of the costly bromine. (c) Search fbr "masked" alkali-labile glycolaldehydes, other than 7. as potential inexpensive precursors of serine. As

Der aus Stigmasterin in 70proz. Ausb. erhältliche Aldehyd (I) geht beim Behandeln mit O2/K‐tert.‐butoxid und Trimethylphosphit in ein Gemisch der Alkohole (II) und (III) über.

Reaction of (20S)-5a-chloro-3~-hydroxypregnane-20-carboxaldehyde (9, prepared in two steps from stigmasterol) with oxygen and potassium terf-butoxide, followed by trimethyl phosphite treatment, afforded 5a-chlorc-3~,17a-dihydroxypregnan-20-one (6) and 3P.17a-dihydroxypregn-5-en-20-one (7). This mixture was converted into 7 by potassium hydroxide treatment, and into 17a-hydroxypregn-4-ene-3,20-dione (8) by reaction with pyridinium dichromate followed by potassium hydroxide treatment. Bromination-dehydrobromination of 9, in one or two steps, afforded ( Z ) -and (E)-5a-chloro-3~-hydroxypregn-l7(20)-ene-20-carboxaldehyde (11). Reaction of 11 with oxygen and potassium hydroxide gave 5a-chloro-3P-hydroxypregn-16-en-20-one (12), which was converted to 3P-hydroxypregna-l5,6-dien-2@one (13) by further potassium hydroxide treatment, and to pregna-4,16-diene-3,20-dione (14) by Oppenauer reaction using excess aluminium isopropoxide. The conversion of derivatives of stigmasterol, an abundant raw material, to 20-keto (3) and 17a-hydroxy-20-keto (5) steroids is well known; of the reported methods, the more valuable are, to our knowledge, those illustrated with partial formulas in scheme 1 (as starting materials 1, several stigmast-22-ene derivatives can be used). Einfache Urnwandlung einesHowever, a still better valorization of the intermediates 2 would result from (a) their direct conversion into derivatives 5, the latter being more valuable than those of type 3, and (b) their ready conversion into pregn-16-en-20-ones6)", which are the most versatile

On treatment of vinyl chloride epoxide (4) with water, of chloroethylene carbonate (9) with aqueous bases, of vinyl acetate (1) or ethyl vinyl ether (6) with aqueous potassium chlorate and catalytic amounts of osmium tetroxide, glycolaldehyde (5) was formed (scheme 1). The not isolated aldehyde 5, when submitted to the Zelinsky‐Stadnikoff amino acid synthesis, afforded DL‐serine in 70% yield. The latter method, when applied directly to the “masked” glycolaldehydes 2, 7, 9, 10, vinylene carbonate (11), 13 or 14, also gave DL‐serine (yields 35–70%), whereas with 4 no serine formation could be detected (scheme 1).